Coating composition and articles coated therewith

ABSTRACT

The present invention relates to a binder useful in coating end uses. The binder preferably includes an aqueous polymer dispersion and a vinyl polymer. The binder is useful in packaging coatings, including coatings for use on food or beverage cans, or a portion thereof.

CROSS REFERENCE TO RELATED APPLICATION

This application is continuation of U.S. application Ser. No. 13/384,308filed Feb. 22, 2012 (now U.S. Pat. No. 8,747,979) which is the NationalStage filing under 35 U.S.C. 371 of International Application No.PCT/US2010/042254 filed Jul. 16, 2010 and entitled “COATING COMPOSITIONAND ARTICLES COATED THEREWITH,” which claims the benefit of U.S.Provisional Application Ser. No. 61/226,547 filed Jul. 17, 2009 andentitled “COATING COMPOSITIONS FOR CANS AND METHODS OF COATING” and U.S.Provisional Application Ser. No. 61/243,888 filed Sep. 18, 2009 andentitled “COATING COMPOSITION AND ARTICLES COATED THEREWITH,” thedisclosures of which are incorporated herein in their entirety.

FIELD OF INVENTION

The present invention relates to a coating composition useful forcoating a variety of substrates, including packaging articles.

BACKGROUND

A wide variety of coatings have been used to coat the surfaces ofpackaging articles (e.g., food and beverage cans). For example, metalcans are sometimes coated using “coil coating” or “sheet coating”operations, i.e., a planar coil or sheet of a suitable substrate (e.g.,steel or aluminum metal) is coated with a suitable composition andhardened (e.g., cured). The coated substrate then is formed into the canend or body. Alternatively, liquid coating compositions may be applied(e.g., by spraying, dipping, rolling, etc.) to the formed article andthen hardened (e.g., cured).

Packaging coatings should preferably be capable of high-speedapplication to the substrate and provide the necessary properties whenhardened to perform in this demanding end use. For example, the coatingshould be safe for food contact, have excellent adhesion to thesubstrate, and resist degradation over long periods of time, even whenexposed to harsh environments.

Various coatings have been used as interior protective can coatings,including epoxy-based coatings and polyvinyl-chloride-based coatings.Each of these coating types, however, has potential shortcomings. Forexample, the recycling of materials containing polyvinyl chloride orrelated halide-containing vinyl polymers can be problematic. There isalso a desire by some to reduce or eliminate certain epoxy compoundscommonly used to formulate food-contact epoxy coatings.

What is needed in the marketplace is an improved binder system for usein coatings such as, for example, packaging coatings.

SUMMARY

The invention provides a coating composition for use with a variety ofarticles, including metal packaging articles such as food or beveragecans. In preferred embodiments, the coating composition includes anaqueous dispersion that includes (i) a water-dispersible polymer suchas, e.g., a polyurethane polymer, a polyester polymer, an alkyd polymer,an acrylic polymer, or a mixture or copolymer thereof and (ii) a vinylpolymer. For sake of convenience, the water-dispersible polymer and thevinyl polymer are referred to collectively herein as a “binder.” Incertain preferred embodiments, the vinyl polymer is formed in thepresence of an aqueous dispersion of the water-dispersible polymer, morepreferably the vinyl polymer is emulsion polymerized in the presence ofthe aqueous dispersion. In some embodiments, the vinyl polymer has anumber average molecular weight of at least 100,000, more preferably atleast 200,000, and even more preferably at least 300,000.

The water-dispersible polymer (preferably a polyurethane) and the vinylpolymer may be present in the same and/or different particles of anaqueous dispersion. The water-dispersible polymer and the vinyl polymercan be present as separate polymers (i.e., polymers that are notcovalently attached to one another), covalently attached polymers, or amixture thereof. Optional covalent linkages may be formed between thewater-dispersible polymer and the vinyl polymer at any suitable time,including prior to cure (e.g., during formation of the vinyl polymer),during and/or after cure of a coating composition including the binder,or a combination thereof. In some embodiments, the water-dispersiblepolymer and the vinyl polymer are not covalently attached while presentin one or both of a liquid coating composition or a cured coatingresulting therefrom.

In preferred embodiments, the coating composition includes both apolyurethane polymer and a vinyl polymer. The polyurethane polymer maybe a polyurethane-urea polymer, which preferably has a plurality ofurethane and urea linkages. Preferably at least some of the urea andurethane linkages are located in a backbone of the polymer.

In some embodiments, the water-dispersible polymer includes one or moreoptional aliphatic carbon-carbon double bonds. In one such embodiment,the polymer (preferably a polyurethane) includes one or more(poly)alkene groups, and more preferably one or more backbone(poly)alkene segments.

The invention also provides a method for making a binder, as well as amethod for making a coating composition including the binder. In oneembodiment, the invention provides a method for making a binder thatincludes the steps of providing an aqueous dispersion of apolyurethane-urea polymer, more preferably a polyurethane-urea salt, andforming a vinyl polymer in the presence of the aqueous dispersion of thepolyurethane-urea polymer. In one embodiment, the vinyl polymer is batchpolymerized in the presence of the polyurethane polymer.

The invention also provides articles having the coating composition ofthe invention disposed on at least a portion thereof (e.g., as a primercoat, an intermediate coat, and/or a topcoat). In some embodiments, thecoated article is a food or beverage can or a portion thereof. Thecoating composition of the invention may be applied on any surface ofthe food or beverage can, including a food-contact surface. The coatingcomposition may be applied on a substrate (typically a metal substrate)either prior to or after forming the substrate, e.g., into a can or aportion thereof.

DEFINITIONS

The term “substantially free” of a particular mobile compound means thatthe compositions of the present invention contain less than 1000 partsper million (ppm) of the recited mobile compound. The term “essentiallyfree” of a particular mobile compound means that the compositions of thepresent invention contain less than 100 parts per million (ppm) of therecited mobile compound. The term “essentially completely free” of aparticular mobile compound means that the compositions of the presentinvention contain less than 5 parts per million (ppm) of the recitedmobile compound. The term “completely free” of a particular mobilecompound means that the compositions of the present invention containless than 20 parts per billion (ppb) of the recited mobile compound.

The term “mobile” means that the compound can be extracted from thecured coating when a coating (typically ˜1 mg/cm² (6.5 mg/in²) thick) isexposed to a test medium for some defined set of conditions, dependingon the end use. An example of these testing conditions is exposure ofthe cured coating to HPLC-grade acetonitrile for 24 hours at 25° C.

If the aforementioned phrases are used without the term “mobile” (e.g.,“substantially free of XYZ compound”) then the compositions of thepresent invention contain less than the aforementioned amount of thecompound whether the compound is mobile in the coating or bound to aconstituent of the coating.

A group that may be the same or different is referred to as being“independently” something.

Substitution is anticipated on the organic groups of the compounds ofthe present invention. As a means of simplifying the discussion andrecitation of certain terminology used throughout this application, theterms “group” and “moiety” are used to differentiate between chemicalspecies that allow for substitution or that may be substituted and thosethat do not allow or may not be so substituted. Thus, when the term“group” is used to describe a chemical substituent, the describedchemical material includes the unsubstituted group and that group withO, N, Si, or S atoms, for example, in the chain (as in an alkoxy group)as well as carbonyl groups or other conventional substitution. Where theterm “moiety” is used to describe a chemical compound or substituent,only an unsubstituted chemical material is intended to be included. Forexample, the phrase “alkyl group” is intended to include not only pureopen chain saturated hydrocarbon alkyl substituents, such as methyl,ethyl, propyl, t-butyl, and the like, but also alkyl substituentsbearing further substituents known in the art, such as hydroxy, alkoxy,alkylsulfonyl, halogen atoms, cyano, nitro, amino, carboxyl, etc. Thus,“alkyl group” includes ether groups, haloalkyls, nitroalkyls,carboxyalkyls, hydroxyalkyls, sulfoalkyls, etc. On the other hand, thephrase “alkyl moiety” is limited to the inclusion of only pure openchain saturated hydrocarbon alkyl substituents, such as methyl, ethyl,propyl, t-butyl, and the like. As used herein, the term “group” isintended to be a recitation of both the particular moiety, as well as arecitation of the broader class of substituted and unsubstitutedstructures that encompasses the moiety.

The term “aliphatic” when used in the context of a carbon-carbon doublebond includes both linear aliphatic and cycloaliphatic carbon-carbondouble bonds, but excludes carbon-carbon double bonds of aromatic rings.

The term “unsaturation” when used in the context of a compound refers toa compound that includes at least one non-aromatic (e.g., aliphatic)double or triple bond.

The term “vinyl polymer” refers to a polymer prepared by additionpolymerizing an ethylenically unsaturated component (e.g., a mixture ofethylenically unsaturated monomers and/or oligomers).

The term “(meth)acrylate” includes both acrylates and methacrylates.

The term “polymer” includes both homopolymers and copolymers (i.e.,polymers of two or more different monomers).

The term “dispersion” in the context of a dispersible polymer refers tothe mixture of a dispersible polymer and a carrier. The term“dispersion” is intended to include the term “solution.”

The term “on,” when used in the context of a coating applied on asurface or substrate, includes both coatings applied directly orindirectly to the surface or substrate. Thus, for example, a coatingapplied to a primer layer overlying a substrate constitutes a coatingapplied on the substrate.

The term “food-contact surface” refers to a surface of an article (e.g.,a food or beverage container) that is in contact with, or suitable forcontact with a food or beverage product.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

The terms “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the invention.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably. Thus, for example, a coating composition thatcomprises “a” polymer can be interpreted to mean that the coatingcomposition includes “one or more” polymers.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.). Furthermore, disclosure of a range includesdisclosure of all subranges included within the broader range (e.g., 1to 5 discloses 1 to 4, 1.5 to 4.5, 1 to 2, etc.).

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

This invention provides a coating composition for use on a variety ofsurfaces, including surfaces of metal articles. The coating compositionis particularly useful as a coating for metal packaging articles,including food and beverage cans. The coating composition includes abinder, preferably in a film-forming amount. The binder preferablyincludes (i) a water-dispersible polymer such as, for example, awater-dispersible polyurethane polymer and (ii) a vinyl polymer.

The coating composition can be applied to a metal substrate eitherbefore or after the substrate is formed into an article (e.g., a food orbeverage can) or a portion thereof. Preferred coating compositions ofthe invention are suitable for use in food-contact situations and may beused on the inside of food or beverage cans.

The binder may be formed using any suitable process. In one embodiment,the binder is prepared by polymerizing an ethylenically unsaturatedcomponent in the presence of an aqueous dispersion of awater-dispersible polymer. The ethylenically unsaturated component ispreferably a mixture of one or more monomers and/or oligomers.Preferably, at least one of the monomers and/or oligomers in the mixtureis an alpha, beta-ethylenically unsaturated monomer. The binder may alsobe prepared using any other suitable method, including, for example, bycombining an aqueous polymer dispersion, more preferably a polyurethanedispersion, and a vinyl polymer. It is also contemplated that the bindermay be formed by either (i) polymerizing the water-dispersible polymerin the presence of the vinyl polymer or (ii) simultaneously polymerizingboth the water-dispersible polymer and the ethylenically unsaturatedcomponent. For the above methods (i) or (ii), it is contemplated thatthe water-dispersible polymer may be rendered water dispersible in apost-polymerization step, if desired.

The water-dispersible polymer can be any suitable polymer, including,for example, a polyurethane polymer, a polyester polymer, an alkydpolymer, an acrylic polymer, or any copolymer or combination of theforegoing. Polyurethane polymers are presently preferred for certain enduses (e.g., beverage end coatings) due to the excellent fabricationproperties observed for certain binders of the invention that include awater-dispersible polyurethane polymer. In some embodiments,water-dispersible polyurethane-urea polymers are preferred. For purposesof convenience, the water-dispersible polymer of the aqueous dispersionwill hereinafter be discussed primarily in the context of a polyurethanepolymer. It should be understood, however, that the below teachings aregenerally applicable to water-dispersible polymers other thanpolyurethanes. As such, any suitable water-dispersible polymer such as,e.g., a water-dispersible acrylic, polyester, or alkyd may besubstituted for the water-dispersible polyurethane in the belowdescribed binders and coating compositions. For further discussion ofsuitable such polymers see U.S. 2006/0100366 and U.S. application Ser.No. 12/505,255 filed on Jul. 17, 2009 and entitled “COATING COMPOSITIONSFOR CANS AND METHODS OF COATING,” each of which is incorporated hereinby reference.

The polyurethane polymer (which in certain embodiments is apolyurethane-urea polymer) and the vinyl polymer of preferred binders ofthe invention may be present in a variety of different configurations.For example, the polyurethane polymer and the vinyl polymer may bepresent in (i) different particles of an aqueous dispersion (e.g., apolyurethane-containing particle and a separate vinyl-containingpolymer) and/or (ii) a particle containing both the polyurethane polymerand the vinyl polymer. If present in the same particle of an aqueousdispersion, the vinyl polymer and the polyurethane polymer may, or maynot, be covalently attached to one another while present in the aqueousdispersion, depending upon the embodiment. In certain embodiments,covalent linkages may be formed between the polyurethane polymer and thevinyl polymer during and/or after cure of the aqueous coatingcompositions, regardless of whether the polyurethane and vinyl polymersare present in the same or different particles of the aqueousdispersion.

In some embodiments, the water-dispersible polymer (e.g.,water-dispersible polyurethane polymer) supports formation of an aqueousdispersion (e.g., a latex) including the vinyl polymer stably dispersedtherein. While not intending to be bound by any theory, it is believedthat in certain embodiments the water-dispersible polymer functions as apolymeric surfactant to support stable dispersion of the vinyl polymerin an aqueous carrier.

The polyurethane polymers can be made water-dispersible using anysuitable means, including the use of water-dispersing groups such asnon-ionic water-dispersing groups, salt groups (e.g., anionic and/orcationic salt groups), or a combination thereof. Alternatively, asurfactant may be used to render the polyurethane polymer waterdispersible. As used herein, the term “water-dispersing groups” alsoencompasses water-solubilizing groups.

In one embodiment, the coating composition is prepared by: formingand/or providing a water-dispersible polyurethane polymer, dispersingthe polyurethane polymer in a carrier that includes water and anoptional organic solvent to form an aqueous dispersion, combining anethylenically unsaturated component with the aqueous dispersion(preferably, the ethylenically unsaturated component is added to theaqueous dispersion), and polymerizing the ethylenically unsaturatedcomponent in the presence of the aqueous dispersion to form the binder.

Preferred compositions are substantially free of mobile bisphenol A(BPA) and aromatic glycidyl ether compounds (e.g., BADGE, BFDGE, andepoxy novalacs), more preferably essentially free of these compounds,even more preferably essentially completely free of these compounds, andmost preferably completely free of these compounds. The coatingcomposition (and, hence, the binder) is also preferably substantiallyfree of bound BPA and aromatic glycidyl ether compounds, more preferablyessentially free of these compounds, most preferably essentiallycompletely free of these compounds, and optimally completely free ofthese compounds.

Preferred binders are at least substantially “epoxy-free,” morepreferably “epoxy-free.” The term “epoxy-free,” when used herein in thecontext of a polymer, refers to a polymer that does not include any“epoxy backbone segments” (i.e., segments formed from reaction of anepoxy group and a group reactive with an epoxy group). Thus, forexample, a polymer made from ingredients including an epoxy resin wouldnot be considered epoxy-free. Similarly, a polymer having backbonesegments that are the reaction product of a bisphenol (e.g., bisphenolA, bisphenol F, bisphenol S, 4,4′dihydroxy bisphenol, etc.) and ahalohdyrin (e.g., epichlorohydrin) would not be considered epoxy-free.However, a vinyl polymer formed from vinyl monomers and/or oligomersthat include an epoxy moiety (e.g., glycidyl methacrylate) would beconsidered epoxy-free because the vinyl polymer would be free of epoxybackbone segments. The coating composition of the invention is alsopreferably at least substantially epoxy-free, more preferablyepoxy-free.

In preferred embodiments, the binder is “PVC-free,” and preferably thecoating composition is also “PVC-free.” That is, each compositionpreferably contains less than 2 weight percent (“wt-%”) of vinylchloride materials, more preferably less than 0.5 wt-% of vinyl chloridematerials, and even more preferably less than 1 part-per-million ofvinyl chloride materials.

In preferred embodiments, the number average molecular weight (“Mn”) ofthe water-dispersible polyurethane polymer is no greater than 50,000,preferably no greater than 45,000, and even more preferably no greaterthan 40,000. Preferably, the Mn of the water-dispersible polyurethanepolymer is at least 5,000, more preferably at least 10,000, and evenmore preferably at least 30,000.

In preferred embodiments, the water-dispersible polyurethane polymercontains a suitable amount of water-dispersing groups, preferably saltand/or salt-forming groups, to form a stable aqueous dispersion with anaqueous carrier. Non-limiting examples of suitable salt-forming groupsinclude neutralizable groups (e.g., acidic or basic groups).Non-limiting examples of suitable salt groups include anionic saltgroups, cationic salt groups, or combinations thereof. As previouslydiscussed, the polymer can contain non-ionic water-dispersing groups inaddition to, or in place of, salt or salt-forming groups.

The polyurethane polymer is typically dispersed using salt groups. Asalt (which can be a full salt or partial salt) is typically formed byneutralizing or partially neutralizing salt-forming groups of thepolyurethane polymer with a suitable neutralizing agent. Alternatively,the polyurethane polymer may be formed from ingredients includingpreformed salt groups. The degree of neutralization required to form thedesired polymer salt may vary considerably depending upon the amount ofsalt-forming groups included in the polymer, and the degree ofsolubility or dispersibility of the salt which is desired. Ordinarily inmaking the polymer water dispersible, the salt-forming groups (e.g.,acid or base groups) of the polymer are at least 25% neutralized,preferably at least 30% neutralized, and more preferably at least 35%neutralized, with a neutralizing agent in water.

Non-limiting examples of anionic salt groups include neutralized acid oranhydride groups, sulphate groups (—OSO₃ ⁻), phosphate groups (—OPO₃ ⁻),sulfonate groups (—SO₂O⁻), phosphinate groups (—POO⁻), phosphonategroups (—PO₃ ⁻), and combinations thereof. Non-limiting examples ofsuitable cationic salt groups include:

(referred to, respectively, as quaternary ammonium groups, quaternaryphosphonium groups, and tertiary sulfate groups) and combinationsthereof. Non-limiting examples of non-ionic water-dispersing groupsinclude hydrophilic groups such as ethylene oxide groups. Compounds forintroducing the aforementioned groups into polymers are known in theart.

Non-limiting examples of neutralizing agents for forming anionic saltgroups include inorganic and organic bases such as an amine, sodiumhydroxide, potassium hydroxide, lithium hydroxide, ammonia, and mixturesthereof. In certain embodiments, tertiary amines are preferredneutralizing agents. Non-limiting examples of suitable tertiary aminesinclude trimethyl amine, dimethylethanol amine (also known asdimethylamino ethanol), methyldiethanol amine, triethanol amine, ethylmethyl ethanol amine, dimethyl ethyl amine, dimethyl propyl amine,dimethyl 3-hydroxy-1-propyl amine, dimethylbenzyl amine, dimethyl2-hydroxy-1-propyl amine, diethyl methyl amine, dimethyl1-hydroxy-2-propyl amine, triethyl amine, tributyl amine, N-methylmorpholine, and mixtures thereof. Triethyl amine or dimethyl ethanolamine are preferred tertiary amines.

Non-limiting examples of neutralizing agents for forming cationic saltgroups include organic and inorganic acids such as formic acid, aceticacid, hydrochloric acid, sulfuric acid, and combinations thereof.

When acid or anhydride groups are used to impart water-dispersibility,the acid- or anhydride-functional polymer preferably has an acid numberof at least 5, and more preferably at least 40 milligrams (mg) KOH pergram resin. The acid-functional polymer preferably has an acid number ofno greater than 400, and more preferably no greater than 100 mg KOH pergram resin.

Alternatively, a surfactant may be used in place of water-dispersinggroups to aid in dispersing the polyurethane in an aqueous carrier.Non-limiting examples of suitable surfactants compatible with food orbeverage packaging applications include alkyl sulfates (e.g., sodiumlauryl sulfate), ether sulfates, phosphate esters, sulphonates, andtheir various alkali, ammonium, amine salts and aliphatic alcoholethoxylates, alkyl phenol ethoxylates, and mixtures thereof.

The amount of the water-dispersible polyurethane polymer present in thebinder is preferably at least 5 wt-%, more preferably at least 20 wt-%,even more preferably at least 30 wt-%, and optimally at least 35 wt-%.The amount of the water-dispersible polyurethane polymer present in thebinder is preferably no greater than 95 wt-%, preferably no greater than85 wt-%, even more preferably no greater than 70 wt-%, and optimally nogreater than 55 wt-%. These percentages are based on total amount ofvinyl polymer and polyurethane polymer.

The polyurethane polymer preferably includes a sufficient number ofurethane linkages to provide the desired coating properties for thedesired end use. Such coating properties may include flexibility,abrasion resistance, and/or fabrication (e.g., to accommodate the rivetand other contours of a beverage can end without unsuitably cracking orripping). Preferred polyurethane polymers preferably include on averageat least about 2 urethane linkages, more preferably at least 10 urethanelinkages, and even more preferably at least 20 urethane linkages permolecule of the polyurethane polymer. While the number of urethanelinkages present in the polyurethane polymer is not particularlyrestricted on the high end and may vary depending upon molecular weight,in certain embodiments, the polyurethane polymer includes on averageless than 1,000 urethane linkages, less than 200 urethane linkages, orless than 50 urethane linkages per molecule of the polyurethane polymer.

Isocyanate content may be another useful measure of urethane linkagecontent. In presently preferred embodiments, the polyurethane polymer isformed from at least about 0.1 wt-%, more preferably at least about 1wt-%, and even more preferably at least 5 wt-% of an isocyanatecompound. Preferably, the polyurethane polymer is formed from less thanabout 25 wt-%, more preferably less than about 20 wt-%, and even morepreferably less than about 15 wt-% of an isocyanate compound.Preferably, the isocyanate compound is incorporated into a backbone ofthe polyurethane polymer via a urethane linkage, and more preferably apair of urethane linkages.

The polyurethane polymer may include a backbone of any suitablestructural configuration. The backbone can have different structuralconfigurations depending on a variety of factors such as the materialsused to form the backbone, cost, and the desired end use for thepolymer. The backbone may optionally include one or more other backbonelinkages such as, for example, amide, ester, carbonate ester, epoxy,ether, imide, imine, or urea linkages, or a combination thereof.Moreover, the backbone of the polyurethane polymer may optionallyinclude one or more oligomer or polymer segments selected from, forexample, acrylic, polyamide, polyester, poly(carbonate ester), epoxy,polyether, polyimide, polyimine, or polyurea segments, or a combinationthereof.

In certain preferred embodiments, the backbone is a polyurethane-ureabackbone. The polyurethane polymer may include any suitable number ofoptional urea linkages. Preferably at least some of the urea linkagesare located in a backbone of the polyurethane polymer. In someembodiments, the polyurethane polymer includes on average at least about1 urea linkage, more preferably at least 5 urea linkages, and even morepreferably at least 10 urea linkages per molecule of the polyurethanepolymer. While the number of urea linkages present in the polyurethanepolymer is not particularly restricted on the high end and may varydepending upon molecular weight, in certain embodiments, thepolyurethane polymer includes on average less than 1,000 urea linkages,less than 200 urea linkages, or less than 20 urea linkages per moleculeof the polyurethane polymer.

In some embodiments, the polyurethane polymer is a linear, orsubstantially linear, polymer. In other embodiments, the polyurethanepolymer may include branching.

The polyurethane polymer of the invention may be formed using anysuitable reactants and any suitable process. The polyurethane polymer istypically formed by reacting ingredients that include one or moreisocyanate-functional compounds, one or more polyols, and optionally oneor more additional reactants (e.g., organic materials having one or moreactive hydrogen groups).

A variety of isocyanate compounds may be used to form the polyurethanepolymer. In some embodiments, the isocyanates are incorporated into thepolyurethane polymer exclusively through urethane linkages. In otherembodiments, at least some of the isocyanate compound may beincorporated into the backbone of the polyurethane polymer via one ormore non-urethane (e.g., urea) linkages formed through a reactioninvolving an isocyanate group (—NCO) of the isocyanate compound.

The isocyanate compound may be any suitable compound, including anisocyanate compound having 1 isocyanate group; a polyisocyanate having 2isocyanate groups, 3 isocyanate groups, or 4 or more isocyanate groups;or a mixture thereof. Suitable diisocyanates may include isophoronediisocyanate (i.e.,5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane);5-isocyanato-1-(2-isocyanatoeth-1-yl)-1,3,3-trimethylcyclohexane;5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclohexane;5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane;1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane;1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane;1-isocyanato-2-(4-isocy-anatobut-1-yl)cyclohexane;1,2-diisocyanatocyclobutane; 1,3-diisocyanatocyclobutane;1,2-diisocyanatocyclopentane; 1,3-diisocyanatocyclopentane;1,2-diisocyanatocyclohexane; 1,3-diisocyanatocyclohexane;1,4-diisocyanatocyclohexane; dicyclohexylmethane 2,4′-diisocyanate;trimethylene diisocyanate; tetramethylene diisocyanate; pentamethylenediisocyanate; hexamethylene diisocyanate; ethylethylene diisocyanate;trimethylhexane diisocyanate; heptamethylene diisocyanate;2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentyl-cyclohexane; 1,2-, 1,4-,and 1,3-bis(isocyanatomethyl)cyclohexane; 1,2-, 1,4-, and1,3-bis(2-isocyanatoeth-1-yl)cyclohexane;1,3-bis(3-isocyanatoprop-1-yl)cyclohexane; 1,2-, 1,4- or1,3-bis(4-isocyanatobuty-1-yl)cyclohexane; liquidbis(4-isocyanatocyclohexyl)-methane; and derivatives or mixturesthereof.

In some embodiments, the isocyanate compounds are preferablynon-aromatic (e.g., aliphatic). Non-aromatic isocyanates areparticularly desirable for coating compositions intended for use on aninterior surface of a food or beverage can. Isophorone diisocyanate(IPDI) and hexamethylene isocyanate (HMDI) are preferred non-aromaticisocyanates. In certain preferred embodiments, the polyurethane polymerdoes not include any structural units derived from aromatic isocyanatecompounds.

In some embodiments, at least some, or alternatively all, of theisocyanate compounds may be a partially blocked polyisocyanate. Certainembodiments may benefit from the inclusion of blocked isocyanate groupsin the polyurethane polymer as a means for forming covalent linkageswith other components of the coating composition, including, forexample, the polyurethane polymer itself or a crosslinking agent.Preferred partially blocked polyisocyanates contain, on average, atleast about 1.5, more preferably at least about 1.8, and even morepreferably at least about 2 free (or unblocked) isocyanate groups permolecule of partially blocked polyisocyanate. Suitable partially blockedpolyisocyanates preferably contain on average less than about 3, morepreferably less than about 2.5, and even more preferably less than about2.2 free isocyanate groups per molecule of partially blockedpolyisocyanate. Preferred partially blocked polyisocyanates contain, onaverage, at least about 0.5, more preferably at least about 0.7, andeven more preferably at least about 1 blocked isocyanate groups permolecule of partially blocked polyisocyanate. The blocked isocyanategroups of the at least partially blocked polyisocyanate can be anysuitable combination of deblockable and/or non-deblockable isocyanategroups. In some embodiments, all or substantially all of the blockedisocyanate groups are deblockable.

An example of a deblockable isocyanate group is a blocked isocyanategroup where the blocking group, when exposed to suitable film-curingconditions, can either (i) disassociate to liberate a free (i.e.,unblocked) isocyanate group or (ii) be readily displaced or replaced byanother group or component. Deblockable isocyanate groups are preferablycapable of de-blocking under film-curing conditions so that a covalentlinkage can be formed during cure via reaction of the deblockedisocyanate group with another group (e.g., an isocyanate-reactive groupsuch as a hydroxyl group). The other group may be present on thepolyurethane polymer, the vinyl polymer, an optional crosslinker, oranother optional compound. Preferably, at least a substantial portion,and more preferably a majority, of the deblockable isocyanate groups arecapable of de-blocking during exposure to suitable film-curingconditions. For example, a substantial portion (more preferably at leasta majority) of the deblockable isocyanate groups preferably unblock whena metal substrate coated with a coating composition containing thebinder is either (a) heated in a 190° C. oven for about 20 minutes or(b) heated in a 230° C. oven for about 10 seconds. Preferred deblockableisocyanate groups do not readily unblock during prolonged storage atroom temperature, more preferably do not readily unblock at atemperature of less than about 50° C., and even more preferably do notreadily unblock at a temperature of less than about 100° C.

In some embodiments, the partially blocked polyisocyanate is a trimercompound having two free isocyanate groups and one blocked isocyanategroup, more preferably one deblockable isocyanate group. In one suchembodiment, the polyisocyanate compound is a trifunctional “trimer” thatis a trimerization product prepared from on average three diisocyanatemolecules. In another embodiment, the polyisocyanate compound is atrimer prepared from on average three moles of diisocyanate (e.g., HMDI)reacted with one mole of another compound such as, for example, a triol(e.g., trimethylolpropane).

Non-limiting examples of suitable blocking agents include malonates,such as ethyl malonate and diisopropyl malonate; acetylacetone; ethylacetoacetate; 1-phenyl-3-methyl-5-pyrazolone; pyrazole;3-methylpyrazole; 3,5 dimethyl pyrazole; hydroxylamine; thiophenol;caprolactam; pyrocatechol; propyl mercaptan; N-methyl aniline; aminessuch as diphenyl amine and diisopropyl amine; phenol;2,4-diisobutylphenol; methyl ethyl ketoxime; α-pyrrolidone; alcoholssuch as methanol, ethanol, butanol and t-butyl alcohol; ethylene imine;propylene imine; benzotriazoles such as benzotriazole,5-methylbenzotriazole, 6-ethylbenzotriazole, 5-chlorobenzotriazole, and5-nitrobenzotriazole; methyl ethyl ketoxime (MEKO); diisopropylamine(DIPA); and combinations thereof. Presently preferred blocking agentsfor forming deblockable isocyanate groups include 8-caprolactam,diisopropylamine (DIPA), methyl ethyl ketoxime (MEKO), and mixturesthereof. For further discussion of suitable blocking techniques andsuitable blocked polyisocyanate compounds, see published internationalapplication WO 2010/062928 by Doreau et al.

Deblockable isocyanate groups are but one example of functionality thatmay be included on the polyurethane polymer for reaction with othercomponents of the coating composition such as a crosslinking agent. Anysuitable group capable of reacting with a crosslinking agent may beincluded in the polyurethane polymer. Thus, for example, thepolyurethane polymer may include pendant hydroxyl groups in certainembodiments.

Any suitable combination of one or more polyols can be used to form thepolyurethane polymer. The one or more polyols may be a monomer, anoligomer, a polymer, or a mixture thereof. In addition, the one or morepolyols can be a diol, a triol, a polyol having 4 or more hydroxylgroups, or a mixture thereof. Diols are presently preferred.Non-limiting examples of polyols for use as monomers or as ingredientsfor oligomer or polymer polyols include ethylene glycol, propyleneglycol, 1,3-propanediol, glycerol, diethylene glycol, dipropyleneglycol, triethylene glycol, trimethylolpropane, trimethylolethane,tripropylene glycol, neopentyl glycol, pentaerythritol, 1,4-butanediol,hexylene glycol, cyclohexanedimethanol, a polyethylene or polypropyleneglycol, isopropylidene bis(p-phenylene-oxypropanol-2), and mixturesthereof. Non-limiting examples of suitable oligomer and/or polymerpolyols include polyether polyols, polyester polyols, polyether-esterpolyols, polyurea polyols, polyamide polyols, polycarbonate polyols,saturated or unsaturated polyolefin polyols, and combinations thereof.Suitable polyol monomers may include, for example, glycols and/orglycerol.

In some embodiments, the polyurethane polymer is formed through anoptional polyurethane prepolymer intermediate. The polyurethaneprepolymer preferably includes at least one isocyanate group. Morepreferably, the polyurethane prepolymer has at least one terminalisocyanate group, and more preferably at least two terminal isocyanategroups. Such isocyanate-terminated prepolymers may be produced, forexample, by reacting an organic material preferably having at least twoactive hydrogen groups per molecule with an isocyanate compound, morepreferably a polyisocyanate compound such as a diisocyanate.Non-limiting examples of suitable “active hydrogen groups” includegroups having a hydrogen attached to oxygen (O), sulfur (S), and/ornitrogen (N) atoms as in the groups —OH, —COOH, —SH, ═NH, and —NH₂.Non-limiting examples of suitable organic materials may includeacrylics, alkyds, polyesters, polyethers, polyamides, or mixturesthereof, preferably having two or more active hydrogen groups, and morepreferably two or more hydroxyl groups.

In certain preferred embodiments, a polyol is used to form thepolyurethane prepolymer. Preferably, a stoichiometric excess ofisocyanate is reacted with the polyol. Non-limiting examples of suitableequivalents ratio of isocyanate groups to hydroxyl groups range fromabout 1.1:1 to 3:1 (NCO:OH), more preferably from about 1.2:1 to 2.5:1,and even more preferably from about 1.3:1 to 2:1. In one embodiment, adiol is reacted with a diiscocyanate (preferably pursuant to the aboveequivalents ratio) to yield the polyurethane prepolymer.

Presently preferred polyurethane prepolymers have an Mn from about 1,000to about 10,000, more preferably from about 2,500 to about 7,500.

Preferably, the polyurethane prepolymer includes a sufficient number ofsalt and/or salt-forming groups to allow the prepolymer to form a stableaqueous dispersion when combined with an aqueous carrier. The saltand/or salt-forming groups may be any of the groups previouslydiscussed. In some embodiments, a monomer or oligomer having salt orsalt-forming groups may be included in the reactants used to produce thepolyurethane prepolymer. In certain embodiments, an acid- oranhydride-functional, salt-group-forming monomer such as, for example,dimethylolpropionic acid or trimellitic anhydride is used to form theprepolymer. Alternatively, the prepolymer may be reacted with a compoundincluding a salt or salt-forming group.

In some embodiments, the polyurethane prepolymer includes acid oranhydride groups (or other neutralizable groups capable of forminganionic salt groups) that are preferably neutralized with a tertiaryamine. While not intending to be bound by any theory, it is believedthat primary and secondary amines may unsuitably react with isocyanategroups of the prepolymer.

In some embodiments, the polyurethane prepolymer and/or polymer isprepared in a solvent system including reactive diluent. As used herein,the term “reactive diluent” relates to monomers and/or oligomers thatare essentially non-reactive with the polyurethane prepolymer and/orpolymer while present in the solvent phase prior to formation of theaqueous dispersion. As such, the reactive diluent is preferably devoidof groups that may react with ingredients of the polyurethane. Suchgroups may include, for example, isocyanate groups, hydroxyl groups,thiol groups, amine groups, imine groups, etc. The reactive diluentpreferably functions as a solvent or otherwise lowers the viscosity ofthe blend of reactants. In certain embodiments, the use of one or morereactive diluents as a “solvent” can eliminate or reduce the need toincorporate a substantial amount of other cosolvents (such as, e.g.,butanol) during processing. The reactive diluent is preferably capableof undergoing a reaction to form a polymer (typically a vinyl additionpolymer) after dispersing the polyurethane polymer into an aqueouscarrier.

Suitable reactive diluents may include vinyl addition monomers oroligomers such as free-radical reactive monomers and oligomers, monomersor oligomers containing carbonate functionality or glycidylfunctionality, or combinations thereof. In some embodiments, thereactive diluent constitutes a portion, or all, of the ethylenicallyunsaturated component used to produce the vinyl polymer. Reactivediluents useful in the present invention include, for example, vinylcompounds, acrylate compounds, methacrylate compounds, acrylamides,acrylonitriles, and combinations thereof. Suitable vinyl compoundsinclude, for example, vinyl toluene, vinyl acetate, vinyl chloride,vinylidene chloride, styrene, substituted styrenes, isoprene, butadiene,and combinations and oligomers thereof. Suitable (meth)acrylatecompounds may include, for example, butyl acrylate, ethyl acrylate,2-ethylhexyl acrylate, isobutyl acrylate, tert-butyl acrylate, methylacrylate, 2-hydroxyethyl acrylate, poly(ethylene glycol) acrylate,isobornyl acrylate, butyl methacrylate, methyl methacrylate, ethylmethacrylate, isobutyl methacrylate, 2-hydroxyethyl methacrylate,poly(ethylene glycol)methacrylate, poly(propylene glycol) methacrylate,any other suitable (meth)acrylates disclosed herein, and combinationsthereof. Methacrylates are presently preferred.

In some embodiments, the polyurethane prepolymer is optionally chainextended (or otherwise modified) to obtain a higher molecular weightpolyurethane. Chain extension may be achieved by reaction of thepolyurethane prepolymer with one or more chain extenders. This mayoccur, for example, by reacting one or more chain extenders withterminal and/or pendant isocyanate groups present on the polyurethaneprepolymer. Suitable chain extenders may include, for example, alkylamino alcohols, cycloalkyl amino alcohols, heterocyclic amino alcohols,polyamines (e.g., ethylene diamine, diethylene triamine, triethylenetetra amine, melamine, etc.), hydrazine, substituted hydrazine,hydrazide, amides, water, other suitable compounds having activehydrogen groups, ketimines prepared from any of the above amines, andcombinations thereof. Preferably, the chain extension is conducted withorganic polyamines, more preferably aliphatic polyamines having at leasttwo primary amine groups. Diamines are presently preferred. If a chainextender is utilized, the linkage formed between the chain extender andthe polyurethane prepolymer is preferably a urethane or urea linkage,more preferably a urea linkage.

The prepolymer may be chain extended at any suitable time, includingbefore the dispersing step, simultaneous to the dispersing step, afterthe dispersing step, or any combination thereof.

In one embodiment, the prepolymer is chain extended at the same time itis dispersed into an aqueous carrier. While not intending to be bound byany theory, it is believed that simultaneous dispersing and chainextending may result in larger particle sizes, allow for a higherconcentration of organic solvent to be used (if desired), and/or allowfor a higher concentration of solids to be achieved without increasingthe viscosity of the dispersion beyond that which can be easilyprocessed. In addition, simultaneous dispersing and chain extending isconducive to the inclusion of protic solvents, such as alcohols, in thedispersion medium. While not intending to be bound by any theory,significant chain stopping has been observed when chain extendingisocyanate-terminated polyurethane prepolymers in a dispersion mediumcontaining high levels of protic solvent. The observed chain stopping isbelieved to be due to reaction of protic solvent with isocyanate groupsof the polyurethane prepolymer.

As an alternative to the use of chain extenders, the so called “acetoneprocess” may also be used to produce a polyurethane polymer having asuitably high molecular weight. The acetone process of makingpolyurethane polymers involves including a substantial amount of acetonein the reaction mixture used to polymerize a polyurethane polymer (see,e.g., U.S. Pat. No. 4,870,129). The acetone is typically removed (e.g.,via vacuum stripping) after dispersing the resulting polyurethanepolymer in an aqueous carrier. If desired, the acetone process may beused to produce a polyurethane polymer that is free of urea linkages.Nonetheless, if desired, the polyurethane polymer resulting from theacetone process may be chain extended to produce a polyurethane thatoptionally includes urea linkages. In some embodiments, a sulfonatedpolyamine, more preferably a sulfonated diamine, may be used to bothchain extend and incorporate salt and/or salt-forming groups into thepolyurethane resulting from the acetone process. Other suitable organicsolvents that may be useful in the acetone process as a substitute foracetone include non-hydroxyl solvents that preferably have a low boilingpoint and low water solubility. Ketone-containing solvents arepreferred.

As previously discussed, the binder of the invention is preferablyformed by polymerizing the vinyl polymer (e.g., by polymerizing anethylenically unsaturated component) in the presence of an aqueousdispersion, and more preferably in the presence an aqueous polyurethanedispersion. The vinyl polymer may be an acrylic polymer or a non-acrylicvinyl polymer. Typically, the vinyl polymer is formed via vinyl additionpolymerization of an ethylenically unsaturated component. Theethylenically unsaturated component is preferably a mixture of monomersand/or oligomers that are capable of free radical initiatedpolymerization in aqueous medium. It is further contemplated that acationic or anionic polymerization process may be used to form the vinylpolymer.

Suitable ethylenically unsaturated monomers and/or oligomers forinclusion in the ethylenically unsaturated component include, forexample, alkyl (meth)acrylates, vinyl monomers, alkyl esters of maleicor fumaric acid, oligomers thereof, and mixtures thereof.

In certain embodiments, the vinyl polymer is an acrylic-containing vinylpolymer. Suitable alkyl (meth)acrylates include, for example, thosehaving the structure: CH₂═C(R¹)—CO—OR² wherein R¹ is hydrogen or methyl,and R² is an alkyl group preferably containing one to sixteen carbonatoms. The R² group can be substituted with one or more, and typicallyone to three, moieties such as hydroxy, halo, phenyl, and alkoxy, forexample. Suitable alkyl (meth)acrylates therefore encompass hydroxyalkyl (meth)acrylates. The alkyl (meth)acrylate typically is an ester ofacrylic or methacrylic acid. Preferably, R¹ is hydrogen or methyl and R²is an alkyl group having two to eight carbon atoms. Most preferably, R¹is hydrogen or methyl and R² is an alkyl group having two to four carbonatoms.

Suitable alkyl (meth)acrylates include, but are not limited to, methyl(meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl(meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl(meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, decyl(meth)acrylate, isodecyl (meth)acrylate, benzyl (meth)acrylate, lauryl(meth)acrylate, isobornyl (meth)acrylate, octyl (meth)acrylate, nonyl(meth)acrylate, hydroxyethyl acrylate (HEA), hydroxyethyl methacrylate(HEMA), hydroxypropyl (meth)acrylate (HPMA), glycidyl (meth)acrylate(GMA), any other (meth)acrylates disclosed herein, and mixtures thereof.

Difunctional (meth)acrylate monomers may be used in the monomer mixtureas well. Examples include ethylene glycol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, allyl methacrylate, and the like.

Suitable vinyl monomers include, but are not limited to, styrene, methylstyrene, alpha-methylstyrene, halostyrene, isoprene, diallylphthalate,divinylbenzene, conjugated butadiene, vinyl toluene, vinyl naphthalene,and mixtures thereof.

Other suitable polymerizable vinyl monomers for use in the ethylenicallyunsaturated component include acrylonitrile, acrylamide, methacrylamide,methacrylonitrile, vinyl acetate, vinyl propionate, vinyl butyrate,vinyl stearate, N-isobutoxymethyl acrylamide, N-butoxymethyl acrylamide,acrylic acid, methacrylic acid, and mixtures thereof.

Preferably, at least 40 wt-% of the ethylenically unsaturated component,more preferably at least 50 wt-%, will be selected from alkyl acrylatesand methacrylates.

In some embodiments, the ethylenically unsaturated component includesone or more groups capable of forming a covalent linkage with one ormore of the following: another group of the ethylenically unsaturatedcomponent, a group of the water-dispersible polyurethane polymer, agroup of another ingredient of the aqueous dispersion (e.g., acrosslinking agent) and/or the finished coating composition. Someexamples of such groups are provided in a later discussion includedherein.

The amount of vinyl polymer present in the binder is preferably at least5 wt-%, more preferably at least 15 wt-%, even more preferably at least30 wt-%, and optimally at least 45 wt-%. Preferably, vinyl polymerconstitutes no greater than 95 wt-%, more preferably no greater than 80wt-%, even more preferably no greater than 70 wt-%, and optimally nogreater than 65 wt-% of the binder. Such percentages are based on totalweight of vinyl polymer and water-dispersible polyurethane polymer.

As previously discussed, the binder of the invention is preferablyformed by emulsion polymerizing an ethylenically unsaturated componentin the presence of an aqueous dispersion including a water-dispersiblepolymer, more preferably a water-dispersible polyurethane polymer. Withregard to the conditions of the emulsion polymerization, theethylenically unsaturated component is preferably polymerized in aqueousmedium with a water-soluble free radical initiator in the presence ofthe water-dispersible polymer.

The temperature of polymerization of the ethylenically unsaturatedcomponent is typically from 0° C. to 100° C., preferably from 50° C. to90° C., more preferably from 70° C. to 90° C., and even more preferablyfrom 80° C. to 85° C. The pH of the aqueous medium is usually maintainedat a pH of 5 to 12.

The ethylenically unsaturated component may be polymerized with theassistance of a polymerization initiator. For example, a polymerizationinitiator may be employed that thermally decomposes at thepolymerization temperature to generate free radicals. Examples includeboth water-soluble and water-insoluble species. Non-limiting examples ofsuitable free radical initiators include persulfates, such as ammoniumor alkali metal (potassium, sodium or lithium) persulfate; azo compoundssuch as 2,2′-azo-bis(isobutyronitrile),2,2′-azo-bis(2,4-dimethylvaleronitrile), and1-t-butyl-azocyanocyclohexane; hydroperoxides such as t-butylhydroperoxide, hydrogen peroxide, t-amyl hydroperoxide, methylhydroperoxide, and cumene hydroperoxide; peroxides such as benzoylperoxide, caprylyl peroxide, di-t-butyl peroxide, ethyl3,3′-di(t-butylperoxy) butyrate, ethyl 3,3′-di(t-amylperoxy) butyrate,t-amylperoxy-2-ethyl hexanoate, and t-butylperoxy pivilate; peresterssuch as t-butyl peracetate, t-butyl perphthalate, and t-butylperbenzoate; percarbonates, such as di(1-cyano-1-methylethyl)peroxydicarbonate; perphosphates, and the like; and combinations thereof.

Polymerization initiators may be used alone or, alternatively, as theoxidizing component of a redox system. If used, a redox system alsopreferably includes a reducing component such as, for example, ascorbicacid, malic acid, glycolic acid, oxalic acid, lactic acid, thiogycolicacid, or an alkali metal sulfite, more specifically a hydrosulfite,hyposulfite or metabisulfite, such as sodium hydrosulfite, potassiumhyposulfite and potassium metabisulfite, or sodium formaldehydesulfoxylate, and combinations thereof. The reducing component isfrequently referred to as an accelerator or a catalyst activator.

The initiator and accelerator are preferably used in proportion fromabout 0.001 to 5 wt-% each, based on the weight of monomers and/oroligomers to be copolymerized. Promoters such as chloride and sulfatesalts of cobalt, iron, nickel or copper can be used in small amounts, ifdesired. Examples of redox catalyst systems include tert-butylhydroperoxide/sodium formaldehyde sulfoxylate/Fe(II), and ammoniumpersulfate/sodium bisulfite/sodium hydrosulfite/Fe(II).

Chain transfer agents can be used to control polymer molecular weight,if desired.

The polymerization reaction of the ethylenically unsaturated componentto produce the vinyl polymer may be conducted as a batch, intermittent,or continuous operation. In certain embodiments, it is desirable tocharge all, or substantially all, of the ingredients to thepolymerization vessel before commencing polymerization.

In one embodiment, the reactor is charged with an appropriate amount ofwater, water-dispersible polyurethane or other water-dispersiblepolymer, and free radical initiator. The reactor is then heated to thefree radical initiation temperature and charged with the ethylenicallyunsaturated component. Preferably, water, initiator, water-dispersiblepolyurethane polymer, and some portion of the ethylenically unsaturatedcomponent are initially charged to the vessel. There may also be somewater-miscible solvent and/or reactive diluent present. After thisinitial charge is allowed to react for a period of time at thepolymerization temperature, the remaining ethylenically unsaturatedcomponent is added incrementally with the rate of addition being varieddepending on the polymerization temperature, the particular initiatorbeing employed, and the type and amount of monomers being polymerized.After all the monomer component has been charged, a final heating iscarried out to complete the polymerization. The reactor is then cooledand the binder is recovered.

In preferred embodiments, a “batch” process is used to polymerize theethylenically unsaturated component in the presence of the aqueousdispersion. While not intending to be bound by any theory, batchpolymerization of the ethylenically unsaturated component can result ina higher molecular weight vinyl polymer that may yield desirableperformance properties for certain coating end uses such as, forexample, beverage end coatings. In certain preferred embodiments, thevinyl polymer has an Mn of at least about 100,000, more preferably atleast about 200,000, or even more preferably at least about 300,000. Theupper range of the Mn of the vinyl polymer is not restricted and may be1,000,000 or more. In certain embodiments, however, the Mn of thepolymerized ethylenically unsaturated component is less than about1,000,000, or less than about 600,000.

Redox initiation is presently preferred for use in batch polymerizingthe ethylenically unsaturated component.

It is contemplated that the benefits of a batch polymerization processmay also be realized by (i) batch polymerizing, for example, asubstantial portion (e.g., at least a majority) of the ethylenicallyunsaturated component and then later (ii) adding the balance of theethylenically unsaturated component (e.g., through a continuous orintermittent feed) and completing the polymerization. Thus, for example,in certain embodiments, at least about 75 wt-%, more preferably at leastabout 85 wt-%, and even more preferably at least about 95 wt-% of thetotal amount of ethylenically unsaturated component is present asunreacted monomer and/or oligomer in the aqueous dispersion within a1-hour time period (more preferably within a 30-minute time period)during polymerization of the ethylenically unsaturated component, andmore preferably at the same time (e.g., at the onset of polymerizationof the ethylenically unsaturated component). In one embodiment, 100% ofthe total amount of ethylenically unsaturated component is present asunreacted monomer and/or oligomer in the aqueous dispersion at the onsetof polymerization.

Coating compositions of the invention preferably include at least afilm-forming amount of the binder. In preferred embodiments, the coatingcomposition includes at least about 5 wt-%, more preferably at leastabout 15 wt-%, and even more preferably at least about 25 wt-% of thebinder, based on the weight of the binder solids relative to the totalweight of the coating composition. Preferably, the coating compositionincludes less than about 65 wt-%, more preferably less than about 55wt-%, and even more preferably less than about 45 wt-% of the binder,based on the weight of the binder solids relative to the total weight ofthe coating composition.

The binder may optionally include one or more covalent bonds linking thepolyurethane polymer (or other water-dispersible polymer) and the vinylpolymer. While not intending to be bound by any theory, in certainembodiments, the presence of covalent linkages is believed to contributeto one or more improved coating properties. The covalent linkages may beof any suitable form and may be formed at any suitable time using anysuitable reaction mechanism. For example, the covalent bonds may beformed (i) during production of the binder and/or (ii) during, or after,cure of a coating composition containing the binder. In suchembodiments, the polyurethane polymer preferably includes one or morereactive functional groups capable of reacting with one or more reactivefunctional groups of the ethylenically unsaturated component to form acovalent linkage.

A discussion or some representative systems for forming covalentlinkages between the polyurethane polymer and the ethylenicallyunsaturated component is provided below. The discussion is not intendedto be a comprehensive listing of all possible chemistries for formingsuch covalent linkages. It is within the scope of the invention to useother means known in the art to form such covalent linkages.

In some embodiments, the covalent linkages are step-growth linkages(e.g., condensation linkages). Non-limiting examples of suitablecovalent linkages include amide, carbonate ester, ester, epoxy, ether,imide, imine, urea, or urethane linkages, or a combination thereof.Non-limiting examples of suitable functional groups for formingstep-growth linkages include reactive functional group pairs selectedfrom oxirane, hydroxyl (—OH), thiol (—SH), carboxylic (—COOH), amine(—NH₂), imine (═NH), or isocyanate (—NCO), with one functional grouppresent in the polyurethane polymer and the other present in theethylenically unsaturated component and/or the vinyl polymer resultingtherefrom.

Preferably, the covalent linkages are hydrolytically stable, or at leastsubstantially hydrolytically stable. While ester bonds may be used,ester bonds do not typically exhibit good hydrolytic stability.

In one embodiment, an imine linkage may covalently link the polyurethanepolymer and the vinyl polymer. Such an imine linkage may be formed, forexample, by reacting an acetoacetate group and a Schiff base group(e.g., an amine functional group such as a group formed from an adipicdihydrazide group).

In some embodiments, the covalent linkages are substituted orunsubstituted hydrocarbyl linkages. Examples of hydrocarbyl linkagesinclude carbon chains (e.g., substituted or unsubstituted divalent alkylchains such as, e.g., —CH₂CH₂—) formed via reaction of a functionalgroup of the polyurethane polymer and a functional group of theethylenically unsaturated component and/or the resulting vinyl polymer.Hydrocarbyl linkages may be formed, for example, through hydrogenabstraction, free-radical initiated polymerization, a Diels-Alderreaction, Michael Addition, or a combination thereof.

In some embodiments, the ethylenically unsaturated component and/or thepolyurethane polymer includes one or more oxirane moieties. In oneembodiment, the ethylenically unsaturated component used to produce thevinyl polymer includes at least one oxirane group-containing alpha,beta-ethylenically unsaturated monomer and/or oligomer. Such optionalmaterials, when present, are typically included in the ethylenicallyunsaturated component in an amount from 0.1 wt-% to 30 wt-%, morepreferably 1 wt-% to 10 wt-%. Glycidyl methacrylate is an example of apreferred oxirane group-containing alpha, beta-ethylenically unsaturatedmonomer. For further examples of suitable oxirane-functional monomerssee U.S. 2006/0100366. Preferably, at least one of the polyurethanepolymer and the vinyl polymer includes an oxirane group and at least theother includes an acid and/or anhydride group. The reaction of tertiaryamines with materials containing oxirane groups, when carried out in thepresence of water, can afford a product that contains both a hydroxylgroup and a quaternary ammonium hydroxide. Under preferred conditions,an acid group, an oxirane group, and an amine form a quaternary salt.This linkage is favored in certain embodiments (e.g., over esterlinkages), as it not only links the polyurethane and vinyl polymer butpromotes water dispersibility of the joined polymer. (It should be notedthat an acid group and an oxirane group may also form an ester. Some ofthis reaction is possible, though this linkage is typically lessdesirable when water dispersibility is sought.) For further discussionregarding quaternary ammonium salt groups and suitable conditions forforming such groups see U.S. 2006/0100366.

In some embodiments, the vinyl polymer and the polyurethane polymer aregrafted together through a reaction involving an aliphatic carbon-carbondouble bond present in the polyurethane polymer. Grafting may beachieved through the aliphatic carbon-carbon double bond using, forexample, a free-radical initiated polymerization process.

Aliphatic carbon-carbon double bonds may be introduced into thepolyurethane polymer using any suitable compound. The aliphaticcarbon-carbon double bonds may be included in a backbone segment of thepolyurethane, a pendant group of the polyurethane, or a combination ofboth. Preferably, the aliphatic carbon-carbon double bonds are capableof participating in one or more of the following reactions: aDiels-Alder reaction, a free-radical initiated polymerization, a MichaelAddition, or an ionic polymerization. In certain embodiments, aliphaticcarbon-carbon double bonds may be introduced into the polyurethane usinga compound having one or more active hydrogen groups (e.g., —OH, —SH,—COOH, —NH₂, ═NH, etc.) and one or more aliphatic carbon-carbon doublebonds. Non-limiting examples of such compounds include acid oranhydride-functional compounds such as maleic anhydride, itaconicanhydride, nonenylsuccinic anhydride, citraconic anhydride, fumaricanhydride, and acid or ester variants thereof; functionalized(poly)alkenes such as functionalized (poly)butadiene (e.g., hydroxylatedpolybutadiene) or functionalized unsaturated fatty acids (e.g., mono- orpolyunsaturated fatty acids such as arichidonic, eleostearic, erucic,licanic, linoleic, linolenic, oleic, palmitoleic, ricinoleic acid, andmixtures thereof); functionalized alpha, beta ethylenically unsaturatedmonomers (e.g., acrylic acid, methacrylic acid, acrylamide,methacrylamide, hydroxy ethyl acrylate, hydroxy propyl acrylate, hydroxypropyl methacrylate, glycidyl acrylate, or glycidyl methacrylate); orcombinations thereof.

In one embodiment, a hydroxyl group of a hydroxy-functionalized alpha,beta ethylenically unsaturated monomer such as hydroxy propylmethacrylate is reacted with a terminal isocyanate group of thepolyurethane polymer. The resulting unsaturated end group may be used tograft together the polyurethane polymer and the ethylenicallyunsaturated component (e.g., using a free radical initiated process).

The polyurethane polymer can include one or more optional alkene orpolyalkene groups (referred to collectively herein as “(poly)alkene”groups), more preferably one or more (poly)alkene moieties, having atleast one aliphatic carbon-carbon double bond. In certain embodiments,the inclusion of (poly)alkene groups has been observed to yield adesirable balance of coating properties such as good hardness, goodchemical resistance, and good flexibility. While not intending to bebound by any theory, it is believed that the presence of (poly)alkenegroups such as, e.g., polybutadiene contributes to the formation ofcrosslinks (upon coating cure) between (poly)alkene groups of thepolyurethane polymer (either intra-polymer crosslinks within the samepolymer strand or crosslinks between separate polymer strands). In someembodiments, (poly)alkene groups having at least some vinyliccarbon-carbon double bonds are preferred.

The (poly)alkene groups may be substituted or unsubstituted. Moreover,the (poly)alkene groups may be backbone groups or pendant groups.Non-limiting examples of suitable (poly)alkene groups include groupsformed from functionalized butadiene or polybutadiene, unsaturated fattyacids (e.g., mono- or polyunsaturated fatty acids such as arichidonic,eleostearic, erucic, licanic, linoleic, linolenic, oleic, palmitoleic,ricinoleic acid, and mixtures thereof), polyisoprene, poly-EPDM(ethylene propylene diene monomer), modified poly-EPDM (e.g., modifiedwith dicyclopentadiene, vinyl norbornene, etc.), or a combinationthereof. Fully hydrogenated (poly)alkene groups, such as for examplebackbone segments formed from fully hydrogenated polybutadienecompounds, are not (poly)alkene groups.

When present, the (poly)alkene groups are preferably included in anamount of at least about 1 wt-%, more preferably at least about 5 wt-%,and even more preferably at least about 15 wt-%, based on the totalweight of the polyurethane polymer. The (poly)alkene groups arepreferably included in an amount of less than about 80 wt-%, morepreferably less than about 50 wt-%, and even more preferably less thanabout 20 wt-%, based on the total weight of the polyurethane polymer.

Iodine value is another useful measure for characterizing the averagenumber of aliphatic (including cycloaliphatic) carbon-carbon doublebonds present in a material. The polyurethane polymer may have anysuitable iodine value to achieve the desired result. In someembodiments, the polyurethane polymer has an iodine value of at leastabout 10, more preferably at least about 20, even more preferably atleast about 35, and optimally at least about 50. The upper range ofsuitable iodine values is not limited, but in most embodiments theiodine value typically will not exceed about 120, more typically willnot exceed about 100, even more typically will not exceed about 80. Theaforementioned iodine values correspond to the number of grams of iodinethat will react with the double bonds present in 100 grams of thematerial tested. Iodine values may be determined, for example, usingASTM D 5758-02 (Reapproved 2006) entitled “Standard Method forDetermination of Iodine Values of Tall Oil Fatty Acids,” and areexpressed in terms of mole equivalents of iodine per 100 grams of resin.

In embodiments utilizing (poly)alkene groups, an optional metal catalystmay be included in the composition to assist in covalent bond formation.Non-limiting examples of suitable oxidation catalysts include transitionmetals, complexes of transition metals, photoinitiators and the like,and mixtures thereof.

Suitable transition metals may include cobalt, iron, nickel, aluminum,ruthenium, rhodium, palladium, antimony, osmium, iridium, platinum,copper, manganese, and zinc, as well as oxides, salts or complexes ofthese metals, and mixtures thereof. For example, cobalt II salts ofshort chain acids such as acetic acid or terephthalic acid, or longchain acids such as neodecanoic, stearic, 2-ethyl hexanoic, or octenylsuccinic acid may be used. Salts of inorganic acids may also be used.For example, antimony chloride III, antimony chloride V, and cobaltchloride may be used. Preferred catalysts include salts of cobalt andlong chain acids such as, for example, cobalt acetate, cobaltneodecanoate, cobalt stearate, cobalt octoate, and mixtures thereof. Asan alternative and/or supplement to the above metal catalysts, thepolyurethane polymer may include one or more optional ether linkages.

The (poly)alkene groups may be introduced into the polyurethane polymerusing any suitable means. For example, the (poly)alkene groups may beintroduced via reaction with one or more reactants used to form thepolymer. Alternatively, the polyurethane polymer may be post-modified toinclude the (poly)alkene groups. The (poly)alkene groups may bemonovalent or polyvalent (e.g., divalent or trivalent), preferablymonovalent or divalent, more preferably divalent.

The (poly)alkene groups may be incorporated using any suitable reactionprocess. By way of example, the following reaction pathways may be used:step-growth reactions (e.g., condensation reactions), free radicalinitiated reactions, Diels-Alder reactions, etc. Non-limiting examplesof suitable groups for linking the (poly)alkene segment to one or moreother portions of the polyurethane polymer include any of the linkagesgroups disclosed herein, including, for example, step-growth orhydrocarbyl linkages.

In some embodiments, the (poly)alkene group may be incorporated into thepolymer via reaction of (i) one or more active hydrogen groups presentin a compound containing the (poly)alkene with (ii) a counterpart activehydrogen group present on the polymer or a reactant used to form thepolymer. Non-limiting examples of suitable active hydrogen groupsinclude any of the active hydrogen groups disclosed herein.

The following are some examples of methods for introducing (poly)alkenegroups into the polyurethane polymer:

-   -   1. A hydroxyl-functional (poly)alkene may be incorporated into        the polymer via reaction of the hydroxyl groups with isocyanate        and/or carboxylic acid groups present on the polymer or a        reactant used to form the polymer.    -   2. A maleinized (poly)alkene (e.g., a (poly)alkene modified with        maleic anhydride such as maleinized polybutadiene) may be        incorporated into the polymer via reaction of acid and/or        anhydride groups with hydroxyl groups present on the polymer or        a reactant used to form the polymer.    -   3. A maleinized (poly)alkene (e.g., maleinized polybutadiene)        may be incorporated into a polymer through hydrolysis of an        anhydride group and subsequent epoxy esterification with a group        present on the polymer or a reactant used to form the polymer.    -   4. A maleinized (poly)alkene (e.g., maleinized polybutadiene)        may be incorporated into the polymer via amide formation through        reaction of the acid/anhydride group with a primary amine group        on the polymer or a reactant used to form the polymer.    -   5. An epoxy-functional (poly)alkene may be incorporated into the        polymer through reaction of an epoxy group with a carboxylic        acid group present on the polymer or a reactant used to form the        polymer, or through quaternary ammonium salt formation.    -   6. A (poly)alkene having acrylic or methacrylic functionality        may be incorporated into the polymer or a reactant used to form        the polymer via free radical polymerization.    -   7. A carboxylic acid-functional (poly)alkene may be incorporated        into the polymer or a reactant used to form the polymer via        esterification with hydroxyls or epoxy esterification with        oxirane groups.

(Poly)butadiene groups, and polybutadiene backbone segments inparticular, are preferred (poly)alkene groups. Hydroxyl-terminatedpolybutadiene is a presently preferred compound for forming (poly)alkenegroups. In one embodiment, hydroxyl-terminated polybutadiene is includedin the reactants used to form the water-dispersible polyurethanepolymer.

In some embodiments, unsaturated cyclic groups, more preferablyunsaturated polycyclic groups (i.e., at least bicyclic groups) such as,for example, unsaturated bicyclic groups (e.g., norbornene groups), maybe included in the polyurethane polymer either in place of and/or inaddition to the optional (poly)alkene groups. In one embodiment, theunsaturated polycyclic group includes a bicyclic structure representedby the IUPAC (International Union of Pure and Applied Chemistry)nomenclature of the below Expression (I):bicyclo[x.y.z]alkene

In Expression (I),

-   -   x is an integer having a value of 2 or more,    -   y is an integer having a value of 1 or more,    -   z is an integer having a value of 0 or more, and    -   the term alkene refers to the IUPAC nomenclature designation        (e.g., hexene, heptene, heptadiene, octene, etc.) for a given        bicyclic molecule and denotes that the bicyclic group includes        one or more double bonds (e.g. ≧1, ≧2, ≧3 double bonds).

Preferably z in Expression (I) is 1 or more. In other words, preferredbicyclic groups include a bridge with a least one atom (typically one ormore carbon atoms) interposed between a pair of bridgehead atoms, wherethe at least one atom is shared by at least two rings. By way ofexample, bicyclo[4.4.0]decane does not include such a bridge.

In preferred embodiments, x has a value of 2 or 3 (more preferably 2)and each of y and z independently have a value of 1 or 2.

Non-limiting examples of some suitable groups represented by Expression(I) include monovalent or polyvalent (e.g., divalent) variants ofbicyclo[2.1.1]hexene, bicyclo[2.2.1]heptene (i.e., norbornene),bicyclo[2.2.2]octene, bicyclo[2.2.1]heptadiene, andbicyclo[2.2.2]octadiene. Bicyclo[2.2.1]heptene is a presently preferredunsaturated polycyclic group.

It is contemplated that the unsaturated cyclic groups represented byExpression (I) may contain one or more heteroatoms (e.g., nitrogen,oxygen, sulfur, etc.) and may be substituted to contain one or moreadditional substituents. For example, one or more cyclic groups(including, e.g., pendant cyclic groups and ring groups fused to a ringof a bicyclic UC group) or acyclic groups may be attached to thebicyclic group represented by Expression (I). Thus, for example, in someembodiments the bicyclic group of Expression (I) may be present in atricyclic or higher group.

A discussion of materials and methods for introducing unsaturated cyclicgroups into polymers, including unsaturated bicyclic groups, is providedin International Application No. PCT/US2010/030584 filed on Apr. 9, 2010and entitled “Polymer Having Unsaturated Cycloaliphatic Functionalityand Coating Compositions Formed Therefrom.” By way of example, aDiels-Alder reaction may be used to modify an unsaturated polyurethane(e.g., using cyclopentadiene or dicyclopentadiene) to include anunsaturated bicyclic group. Alternatively, the polyurethane polymer maybe formed using reactants having unsaturated polycyclic groups such as,for example, nadic acid or anhydride, methyl-nadic acid or anhydride,tetrahydrophthalic acid or anhydride, methyltetrahydrophthalic acid oranhydride, and mixtures thereof.

As previously discussed, the coating composition of the inventionpreferably includes water and may further include one or more optionalorganic solvents. Preferably, the coating composition includes at leastabout 20 wt-%, more preferably at least about 25 wt-%, and even morepreferably at least about 30 wt-% of water, based on the weight of thecoating composition. In some embodiments, the coating compositionincludes less than about 90 wt-%, more preferably less than about 60wt-%, and even more preferably less than about 40 wt-% of water, basedon the total weight of the coating composition.

In certain embodiments, the coating composition preferably includes oneor more organic solvents in an amount of at least about 10 wt-%, morepreferably at least about 20 wt-%, and even more preferably at leastabout 25 wt-%, based on the weight of the coating composition. In someembodiments, the coating composition includes less than about 70 wt-%,more preferably less than about 60 wt-%, and even more preferably lessthan about 45 wt-% of organic solvent, based on the total weight of thecoating composition. While not intending to be bound by any theory, theinclusion of a suitable amount of organic solvent is advantageous, forexample, for certain coil coating applications to modify flow andleveling of the coating composition, control blistering, and maximizethe line speed of the coil coater. Moreover, vapors generated fromevaporation of the organic solvent during cure of the coating may beused to fuel the curing ovens.

The ratio of water to optional organic solvent in the coatingcomposition can vary widely depending on the particular coating end useand application methodology. In some embodiments the weight ratio ofwater to organic solvent in the final coating composition ranges fromabout 0.1:1 to 10:1, (water:organic solvent) more preferably from about0.2:1 to 5:1, and even more preferably from about 0.7:1 to 1.3:1.

The coating composition preferably has a total solids content of fromabout 10 to about 70 wt-%, more preferably from about 20 to about 50wt-%, and even more preferably from about 30 to about 40 wt-%, based onthe weight of the coating composition.

In one embodiment, the coating composition includes 5 to 65 wt-% of thebinder (more preferably 15 to 55 wt-%, even more preferably 25 to 45wt-%), 20 to 60 wt-% of water (more preferably 25 to 50 wt-%, even morepreferably 30 to 40 wt-%), and 10 to 70 wt-% of organic solvent (morepreferably 20 to 60 wt-%, even more preferably 25 to 45 wt-%).

Coating compositions of the invention may be formulated using one ormore optional curing agents (i.e., crosslinking resins, sometimesreferred to as “crosslinkers”). The choice of particular crosslinkertypically depends on the particular product being formulated.Non-limiting examples of crosslinkers include aminoplasts, phenoplasts,blocked isocyanates, and combinations thereof. Preferred curing agentsare substantially free of mobile BPA and aromatic glycidyl ethercompounds (e.g., BADGE, BFDGE and epoxy novalacs).

The amount of crosslinker included may depend on a variety of factors,including, for example, the type of curing agent, the time andtemperature of the bake, the molecular weight of the polymer, and thedesired coating properties. If used, the crosslinker is typicallypresent in an amount of up to 50 wt-%, preferably up to 30 wt-%, andmore preferably up to 15 wt-%. If used, the crosslinker is typicallypresent in an amount of at least 0.1 wt-%, more preferably at least 1wt-%, and even more preferably at least 1.5 wt-%. These weightpercentages are based upon the total weight of the resin solids in thecoating composition.

Phenoplast resins include the condensation products of aldehydes withphenols. Formaldehyde and acetaldehyde are preferred aldehydes. Variousphenols can be employed such as phenol, cresol, p-phenylphenol,p-tert-butylphenol, p-tert-amylphenol, and cyclopentylphenol.

Aminoplast resins are the condensation products of aldehydes such asformaldehyde, acetaldehyde, crotonaldehyde, and benzaldehyde with aminoor amido group-containing substances such as urea, melamine, andbenzoguanamine. Examples of suitable aminoplast resins include, withoutlimitation, benzoguanamine-formaldehyde resins, melamine-formaldehyderesins, esterified melamine-formaldehyde, and urea-formaldehyde resins.

Condensation products of other amines and amides can also be employedsuch as, for example, aldehyde condensates of triazines, diazines,triazoles, guanadines, guanamines and alkyl- and aryl-substitutedmelamines. Some examples of such compounds are N,N′-dimethyl urea,benzourea, dicyandimide, formaguanamine, acetoguanamine, glycoluril,ammelin 2-chloro-4,6-diamino-1,3,5-triazine,6-methyl-2,4-diamino-1,3,5-triazine, 3,5-diaminotriazole,triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine,3,4,6-tris(ethylamino)-1,3,5-triazine, and the like. While the aldehydeemployed is typically formaldehyde, other similar condensation productscan be made from other aldehydes, such as acetaldehyde, crotonaldehyde,acrolein, benzaldehyde, furfural, glyoxal and the like, and mixturesthereof.

Suitable commercially available amino crosslinking resins include, forexample, CYMEL 301, CYMEL 303, CYMEL 370, CYMEL 373, CYMEL 1131, CYMEL1125, and CYMEL 5010 (all available from Cytec Industries Inc., WestPatterson, N.J.), URAMEX BF 892 (available from DSM, Netherlands),MAPRENAL MF 980, and mixtures thereof.

Non-limiting examples of suitable isocyanate crosslinkers includeblocked or non-blocked aliphatic, cycloaliphatic or aromatic di-, tri-,or poly-valent isocyanates, such as hexamethylene diisocyanate (HMDI),cyclohexyl-1,4-diisocyanate, and the like. Further non-limiting examplesof generally suitable blocked isocyanates include isomers of isophoronediisocyanate, dicyclohexylmethane diisocyanate, toluene diisocyanate,diphenylmethane diisocyanate, phenylene diisocyanate, tetramethyl xylenediisocyanate, xylylene diisocyanate, and mixtures thereof. In someembodiments, blocked isocyanates are used that have an Mn of at leastabout 300, more preferably at least about 650, and even more preferablyat least about 1,000.

Polymeric blocked isocyanates are preferred in certain embodiments. Someexamples of suitable polymeric blocked isocyanates include a biuret orisocyanurate of a diisocyanate, a trifunctional “trimer,” or a mixturethereof. Examples of suitable blocked polymeric isocyanates includeTRIXENE BI 7951, TRIXENE BI 7984, TRIXENE BI 7963, TRIXENE BI 7981(TRIXENE materials are available from Baxenden Chemicals, Ltd.,Accrington, Lancashire, England), DESMODUR BL 3175A, DESMODUR BL3272,DESMODUR BL3370, DESMODUR BL 3475, DESMODUR BL 4265, DESMODUR PL 340,DESMODUR VP LS 2078, DESMODUR VP LS 2117, and DESMODUR VP LS 2352(DESMODUR materials are available from Bayer Corp., Pittsburgh, Pa.,USA), or combinations thereof. Examples of suitable trimers may includea trimerization product prepared from on average three diisocyanatemolecules or a trimer prepared from on average three moles ofdiisocyanate (e.g., HMDI) reacted with one mole of another compound suchas, for example, a triol (e.g., trimethylolpropane).

In some embodiments, the coating composition of the invention, based ontotal resin solids, includes at least 5 wt-% of blocked polymericisocyanate, more preferably from about 5 to about 20 wt-% of blockedpolymeric isocyanate, and even more preferably from about 10 to about 15wt-% of blocked polymeric isocyanate.

A coating composition of the present invention may also include otheroptional polymers that do not adversely affect the coating compositionor a cured coating composition resulting therefrom. Such optionalpolymers are typically included in a coating composition as a fillermaterial, although they can be included as a crosslinking material, orto provide desirable properties. One or more optional polymers (e.g.,filler polymers) can be included in a sufficient amount to serve anintended purpose, but not in such an amount to adversely affect acoating composition or a cured coating composition resulting therefrom.

A coating composition of the present invention may also include otheroptional ingredients that do not adversely affect the coatingcomposition or a cured coating composition resulting therefrom. Suchoptional ingredients include, for example, catalysts, dyes, pigments,toners, extenders, fillers, lubricants, anticorrosion agents, flowcontrol agents, thixotropic agents, dispersing agents, antioxidants,adhesion promoters, light stabilizers, surfactants, and mixturesthereof. Each optional ingredient is included in a sufficient amount toserve its intended purpose, but not in such an amount to adverselyaffect a coating composition or a cured coating composition resultingtherefrom.

One preferred optional ingredient is a catalyst to increase the rate ofcure. Examples of catalyst, include, but are not limited to, strongacids (e.g., dodecylbenzene sulphonic acid (DDBSA, available as CYCAT600 from Cytec), methane sulfonic acid (MSA), p-toluene sulfonic acid(pTSA), dinonylnaphthalene disulfonic acid (DNNDSA), and triflic acid),quaternary ammonium compounds, phosphorous compounds, tin and zinccompounds, and combinations thereof. Specific examples include, but arenot limited to, a tetraalkyl ammonium halide, a tetraalkyl or tetraarylphosphonium iodide or acetate, tin octoate, zinc octoate,triphenylphosphine, and similar catalysts known to persons skilled inthe art. If used, a catalyst is preferably present in an amount of atleast 0.01 wt-%, and more preferably at least 0.1 wt-%, based on theweight of nonvolatile material. If used, a catalyst is preferablypresent in an amount of no greater than 3 wt-%, and more preferably nogreater than 1 wt-%, based on the weight of nonvolatile material in thecoating composition.

Another useful optional ingredient is a lubricant (e.g., a wax), whichfacilitates manufacture of fabricated metal articles (e.g., food orbeverage cans, food or beverage can ends, metal closures for foodcontainers, etc.) by imparting lubricity to sheets of coated metalsubstrate. Non-limiting examples of suitable lubricants include, forexample, natural waxes such as Carnauba wax or lanolin wax,polytetrafluoroethane (PTFE) and polyethylene-type lubricants. If used,a lubricant is preferably present in the coating composition in anamount of at least 0.1 wt-%, and preferably no greater than 2 wt-%, andmore preferably no greater than 1 wt-%, based on the weight ofnonvolatile material in the coating composition.

Another useful optional ingredient is a pigment, such as titaniumdioxide. If used, a pigment is present in the coating composition in anamount of no greater than 70 wt-%, more preferably no greater than 50wt-%, and even more preferably from 0.01 to 40 wt-%, based on the totalweight of nonvolatile material in the coating composition.

Surfactants can be optionally added to the coating composition to aid inflow and wetting of the substrate. Examples of surfactants, include, butare not limited to, nonylphenol polyethers and salts and similarsurfactants known to persons skilled in the art. If used, a surfactantis preferably present in an amount of at least 0.01 wt-%, and morepreferably at least 0.1 wt-%, based on the weight of resin solids. Ifused, a surfactant is preferably present in an amount no greater than 10wt-%, and more preferably no greater than 5 wt-%, based on the weight ofresin solids.

Cured coatings of the invention preferably adhere well to metal (e.g.,steel, tin-free steel (TFS), tin plate, electrolytic tin plate (ETP),aluminum, etc.) and provide high levels of resistance to corrosion ordegradation that may be caused by prolonged exposure to, for example,food or beverage products. The coatings may be applied to any suitablesurface, including inside surfaces of containers, outside surfaces ofcontainers, container ends, and combinations thereof.

Cured coatings of the invention are particularly well suited as adherentcoatings for metal cans or containers, although many other types ofarticles can be coated. Examples of such articles include closures(including, e.g., internal surfaces of twist off caps for food andbeverage containers); crowns; two and three-piece cans (including, e.g.,food and beverage containers); shallow drawn cans; deep drawn cans(including, e.g., multi-stage draw and redraw food cans); can ends(including, e.g., easy open can ends or beer and beverage can ends);monobloc aerosol containers; medical packaging articles (e.g., metereddose inhaler cans, including on drug-contact surfaces); and generalindustrial containers, cans, and can ends.

The coating compositions of the present invention are particularly welladapted for use on food and beverage cans, and particularly beverage canends such as beer or soda can ends (which typically include a rivetportion for attachment of a pulltab to the can end). Preferred coatingcompositions of the invention are particularly suited for use on innermetal surfaces of food or beverage containers (e.g., food-contactsurfaces), including as a topcoat (of a multilayer or monolayer coatingsystem) in direct contact with food or beverage products.

Coating compositions of the invention can be applied on a substrate in asingle coat, or monocoat, system or can constitute one or more layers ofa multi-coat system. The coating compositions can be applied, forexample, either directly to a surface of a substrate or to one or moreintermediate coats (e.g., size coats) applied on the substrate. In someembodiments, the coating composition of the invention is applied as amonocoat directly to, for example, an exterior or interior (i.e.,food-contact) surface of a metal food or beverage can.

The coating composition can be applied to a substrate using any suitableprocedure such as spray coating, roll coating, coil coating, curtaincoating, immersion coating, meniscus coating, kiss coating, bladecoating, knife coating, dip coating, slot coating, slide coating, andthe like, as well as other types of premetered coating. In oneembodiment where the coating is used to coat metal sheets or coils, thecoating can be applied by roll coating. Other commercial coatingapplication and curing methods are also envisioned including, forexample, electrocoating, extrusion coating, laminating, powder coating,and the like.

The coating composition can be applied on a substrate prior to, orafter, forming the substrate into an article. In some embodiments, atleast a portion of a planar substrate is coated with a layer of thecoating composition of the invention, which is then cured before theplanar substrate is formed into an article (e.g., a food or beverage canend). By way of example, in some embodiments, an article such as a foodor beverage is stamped from planar metal substrate having a curedcoating composition of the invention thereon.

After applying the coating composition onto a substrate, the compositioncan be cured using a variety of processes, including, for example, ovenbaking by either conventional or convectional methods, or any othermethod that provides an elevated temperature suitable for curing thecoating. The curing process may be performed in either discrete orcombined steps. For example, substrates can be dried at ambienttemperature to leave the coating compositions in a largelyun-crosslinked state. The coated substrates can then be heated to fullycure the compositions. In certain instances, coating compositions of theinvention can be dried and cured in one step.

The curing process may be performed at any suitable temperature,including, for example, temperatures in the range of about 177° C. toabout 250° C. If metal coil is the substrate to be coated, curing of theapplied coating composition may be conducted, for example, by subjectingthe coated metal to a temperature of about 225° C. to about 250° C. fortypically about 10 to 30 seconds. The cure conditions will varydepending upon the method of application and the intended end use.

Preferred coatings of the present invention display one or more of theproperties described in the Test Methods or Examples sections. Morepreferred coatings of the present invention display one or more of thefollowing properties: adhesion rating of 10; blush rating of at least 7;feathering below 0.2 inches; an initial end continuity of less than 10milliamps (“mA”) (more preferably less than 5, 2, or 1 mA); and afterpasteurization or retort, an end continuity of less than 20 mA.

Some additional embodiments of the invention are provided below:

Embodiment 1: A binder comprising:

an aqueous dispersion of a polymer (e.g., a water-dispersible acrylic,alkyd, polyester, or polyurethane polymer, more preferably awater-dispersible polyurethane polymer) having one or more pendant orbackbone (poly)alkene groups; and

a vinyl polymer.

Embodiment 1.5: A binder comprising

an aqueous dispersion of a polymer, more preferably a water-dispersiblepolyurethane polymer, having 2 or more backbone urethane linkages, morepreferably 10 or more backbone urethane linkages, and even morepreferably 20 or more backbone urethane linkages; and

a vinyl polymer.

Embodiment 2: A binder comprising:

an aqueous dispersion of a polymer (e.g., a water-dispersible acrylic,alkyd, polyester, or polyurethane polymer, more preferably awater-dispersible polyurethane polymer); and

a vinyl polymer;

wherein the polymer of the aqueous dispersion and the vinyl polymer arelinked together by one or more covalent linkages.

Embodiment 2.1: The binder of Embodiment 2 or a sub-embodiment thereof,wherein the one or more covalent linkages is a step-growth linkage(e.g., a condensation linkage), a substituted or unsubstitutedhydrocarbyl linkage, or a combination thereof.

Embodiment 2.2: The binder of Embodiment 2 or a sub-embodiment thereof,wherein the one or more covalent linkages comprises a carbonate ester,ester, epoxy, ether, imide, imine, or urea linkage, or a combinationthereof.

Embodiment 2.3: The binder of Embodiment 2 or a sub-embodiment thereof,wherein the one or more covalent linkages are hydrolytically stable.

Embodiment 2.4: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the binder comprises a latex polymer.

Embodiment 2.5: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the binder comprises an emulsion polymerized latexpolymer.

Embodiment 2.6: The binder of any of Embodiments 1, 1.5, 2 or asub-embodiment thereof, wherein the polymer of the aqueous dispersionhas an Mn of at least 5,000, more preferably at least 10,000, even morepreferably at least 30,000.

Embodiment 2.7: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the vinyl polymer has a M_(n) of at least 100,000, morepreferably at least 200,000, and even more preferably at least 300,000.

Embodiment 2.8: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the polyurethane polymer is present in amountcomprising at least 5 wt-%, more preferably at least 20 wt-%, even morepreferably at least 30 wt-%, and optimally at least 35 wt-%, based onthe total weight of the polyurethane polymer and the vinyl polymer.

Embodiment 2.9: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the vinyl polymer is present in amount comprising atleast 5 wt-%, more preferably at least 15 wt-%, even more preferably atleast 30 wt-%, and optimally at least 45 wt-%, based on the total weightof the polyurethane polymer and the vinyl polymer.

Embodiment 2.10: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the polyurethane polymer is formed from reactantscomprising at least 0.1 wt-%, preferably at least 1 wt-%, and even morepreferably at least 5 wt-% of a mono- or poly-isocyanate compound.

Embodiment 2.11: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the water-dispersible polyurethane polymer is achain-extended polyurethane polymer.

Embodiment 2.12: The binder of Embodiments 2.11, wherein thepolyurethane polymer is chain extended with a polyamine chain extender.

Embodiment 2.13: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof wherein the water-dispersible polyurethane polymer is apolyurethane-urea polymer.

Embodiment 2.14: The binder of Embodiments 1.5 or 2 or a sub-embodimentthereof, wherein the polymer of the aqueous dispersion has one or morependant or backbone (poly)alkene groups.

Embodiment 2.15: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the vinyl polymer is formed by polymerizing anethylenically unsaturated component in the presence of the aqueousdispersion.

Embodiment 2.16: The binder of Embodiments 1 or 2 or a sub-embodimentthereof, wherein the water-dispersible polyurethane polymer includes atleast 2 urethane linkages, more preferably at least 10 urethanelinkages, and even more preferably at least 20 urethane linkages.

Embodiment 2.17: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the water-dispersible polyurethane polymer includes atleast 1 urea linkage, more preferably at least 5 urea linkages, and evenmore preferably at least 10 urea linkages.

Embodiment 2.18: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the water-dispersible polyurethane polymer does notinclude any structural units derived from an aromatic isocyanatecompound.

Embodiment 2.19: The binder of Embodiments 1, 1.5, 2 or a sub-embodimentthereof, wherein the water-dispersible polyurethane polymer includes oneor more unsaturated polycyclic groups, more preferably one or moreunsaturated bicyclic groups, and even more preferably one or morebridged bicyclic groups (e.g., a norbornene-type group).

Embodiment 3: A coating composition comprising:

a binder (or system) of Embodiments 1, 1.5, 2 or a sub-embodimentthereof; and

a liquid carrier.

Embodiment 3.1: The coating composition of Embodiment 3, wherein thecoating composition includes at least 5 wt-%, more preferably at least15 wt-%, and even more preferably at least 25 wt-% of the binder.

Embodiment 3.2: The coating composition of Embodiment 3 or anysub-embodiment thereof, wherein the carrier includes water and anoptional organic solvent.

Embodiment 3.3: The coating composition of Embodiment 3 or anysub-embodiment thereof, wherein the coating composition includes atleast 10 wt-%, more preferably at least 20 wt-%, and even morepreferably at least 25 wt-% of organic solvent.

Embodiment 3.4: The coating composition of Embodiment 3 or anysub-embodiment thereof, wherein the coating composition includes atleast 20 wt-%, more preferably at least 25 wt-%, and even morepreferably at least 30 wt-% of water.

Embodiment 3.5: The coating composition of sub-embodiments 3.1-3.4,wherein the weight ratio of water to organic solvent in the coatingcomposition is from 0.1:1 to 10:1 (water:organic solvent).

Embodiment 3.6: The coating composition of Embodiment 3 or anysub-embodiment thereof, wherein the coating composition is substantiallyfree of bound bisphenol A or aromatic glycidyl ether compounds.

Embodiment 3.7: The coating composition of Embodiment 3 or anysub-embodiment thereof, further comprising a crosslinker, preferably inan amount of at least 1 wt-%, based on the total weight of the coatingcomposition.

Embodiment 3.8: The coating composition of Embodiment 3 or anysub-embodiment thereof, wherein the coating composition, when present onan aluminum beverage can end at a dry film thickness of 7 milligrams persquare inch, passes less than 10 milliamps of current (more preferablyless than 5 milliamps, even more preferably less than 1 milliamps) afterbeing exposed for 4 seconds to a room-temperature electrolyte solutioncontaining 1% by weight of NaCl dissolved in water.

Embodiment 3.9: The coating composition of Embodiment 3 or anysub-embodiment thereof, wherein the coating composition includes one ormore lubricants, preferably in an amount from about 0.1 to 2 wt-%, basedon the weight of nonvolatile material in the coating composition.

Embodiment 4: An article, comprising:

a metal substrate; and

the coating composition of Embodiment 3 or any sub-embodiment thereofdisposed on at least a portion of a surface of the metal substrate.

Embodiment 4.1: The article of Embodiment 4, wherein the articlecomprises a metal packaging can.

Embodiment 4.2: The article of Embodiment 4, wherein the articlecomprises a food or beverage can, or a portion thereof.

Embodiment 4.3: The article of Embodiment 4.2, wherein the coatingcomposition is disposed on a food-contact surface.

Embodiment 4.4: The article of Embodiment 4.2, wherein the coatingcomposition is present as a top coat of a mono-coat or multi-coatcoating system.

Embodiment 4.5: The article of Embodiment 4 or any sub-embodimentthereof, wherein the coating composition comprises a cured coating.

Test Methods

The following test methods may be useful in evaluating the properties ofcoating compositions of the invention.

Solvent Resistance

The extent of “cure” or crosslinking of a coating is measured as aresistance to solvents, such as methyl ethyl ketone (MEK, available fromExxon, Newark, N.J.) or isopropyl alcohol (IPA). This test is performedas described in ASTM D 5402-93. The number of double-rubs (i.e., oneback- and forth motion) is reported. This test if often referred to as“MEK Resistance.”

Adhesion

Adhesion testing is performed to assess whether the coating adheres tothe coated substrate. The adhesion test was performed according to ASTMD 3359-Test Method B, using SCOTCH 610 tape (available from 3M Companyof Saint Paul, Minn.). Adhesion is generally rated on a scale of 0-10where a rating of “10” indicates no adhesion failure, a rating of “9”indicates 90% of the coating remains adhered, a rating of “8” indicates80% of the coating remains adhered, and so on. Adhesion ratings of 10are typically desired for commercially viable coatings.

Blush Resistance

Blush resistance measures the ability of a coating to resist attack byvarious solutions. Typically, blush is measured by the amount of waterabsorbed into a coated film. When the film absorbs water, it generallybecomes cloudy or looks white. Blush is generally measured visuallyusing a scale of 0-10 where a rating of “10” indicates no blush and arating of “0” indicates complete whitening of the film. Blush ratings ofat least 7 are typically desired for commercially viable coatings andoptimally 9 or above.

Process or Retort Resistance

This is a measure of the coating integrity of the coated substrate afterexposure to heat and pressure with a liquid such as water. Retortperformance is not necessarily required for all food and beveragecoatings, but is desirable for some product types that are packed underretort conditions. The procedure is similar to the Sterilization orPasteurization test. Testing is accomplished by subjecting the substrateto heat ranging from 105-130° C. and pressure ranging from 0.7 to 1.05kg/cm² for a period of 15 to 90 minutes. For the present evaluation, thecoated substrate was immersed in deionized water and subjected to heatof 121° C. (250° F.) and pressure of 1.05 kg/cm² for a period of 90minutes. The coated substrate was then tested for adhesion and blush asdescribed above. In food or beverage applications requiring retortperformance, adhesion ratings of 10 and blush ratings of at least 7 aretypically desired for commercially viable coatings.

Feathering

Feathering is a term used to describe the adhesion loss of a coating onthe tab of a beverage can end. When a beverage can is opened, a portionof free film may be present across the opening of the can if the coatingloses adhesion on the tab. This is feathering.

To test feathering, a “tab” is scored on the backside of a coated panel,with the coated side of the panel facing downward. The test piece isthen pasteurized as described under the Pasteurization section below.

After pasteurization, pliers are used to bend the cut “tab” to a90-degree angle away from the coated side of the substrate. The testpiece is then placed on a flat surface, coated side down. The cut “tab”is gripped using pliers and the “tab” is pulled from the test panel atan angle of 180 degrees until it is completely removed. After removingthe “tab,” any coating that extends into the opening on the test panelis measured. The distance of the greatest penetration (feathering) isreported in inches. Coatings for beverage can ends preferably showfeathering below 0.2 inch (0.508 cm), more preferably below 0.1 inch(0.254 cm), most preferably below 0.05 inch (0.127 cm), and optimallybelow 0.02 inch (0.051 cm).

Dowfax Detergent Test

The “Dowfax” test is designed to measure the resistance of a coating toa boiling detergent solution. This is a general test run for beverageend coatings and is mainly used to evaluate adhesion. Historically, thistest was used to indicate problems with the interaction of coating tosubstrate pretreatment. The solution is prepared by mixing 5 ml ofDowfax 2A1 (product of Dow Chemical) into 3000 ml of deionized water.Typically, coated substrate strips are immersed into the boiling Dowfaxsolution for 15 minutes. The strips are then rinsed and cooled indeionized water, dried, and then tested and rated for blush and adhesionas described previously. Preferred beverage end coatings provideadhesion ratings of 10 and blush ratings of at least 4, more preferably6 or above in the Dowfax detergent test.

Sterilization or Pasteurization

The sterilization or pasteurization test determines how a coatingwithstands the processing conditions for different types of foodproducts packaged in a container. Typically, a coated substrate isimmersed in a water bath and heated for 5-60 minutes at temperaturesranging from 65° C. to 100° C. For the present evaluation, the coatedsubstrate was immersed in a deionized water bath for 45 minutes at 85°C. The coated substrate was then removed from the water bath and testedfor coating adhesion and blush as described above. Commercially viablecoatings preferably provide adequate pasteurization resistance withperfect adhesion (rating of 10) and blush ratings of at least 5,optimally at least 9.

Fabrication or End Continuity

This test measures the ability of a coated substrate to retain itsintegrity as it undergoes the formation process necessary to produce abeverage can end. It is a measure of the presence or absence of cracksor fractures in the formed end. The end is typically placed on a cupfilled with an electrolyte solution. The cup is inverted to expose thesurface of the end to the electrolyte solution. The amount of electricalcurrent that passes through the end is then measured. If the coatingremains intact (no cracks or fractures) after fabrication, minimalcurrent will pass through the end.

For the present evaluation, fully converted 202 standard openingbeverage can ends were exposed for a period of 4 seconds to aroom-temperature electrolyte solution comprised of 1% NaCl by weight indeionized water. The coating to be evaluated was present on the interiorsurface of the beverage end at a dry film thickness of 6 to 7.5milligrams per square inch (“msi”) (or 9.3 to 11.6 grams per squaremeter), with 7 msi being the target thickness. Metal exposure wasmeasured using a WACO Enamel Rater II, available from theWilkens-Anderson Company, Chicago, Ill., with an output voltage of 6.3volts. The measured electrical current, in milliamps, is reported. Endcontinuities are typically tested initially and then after the ends aresubjected to pasteurization or retort.

Preferred coatings of the present invention initially pass less than 10mA when tested as described above, more preferably less than 5 mA, mostpreferably less than 2 mA, and optimally less than 1 mA. Afterpasteurization or retort, preferred coatings give continuities of lessthan 20 mA, more preferably less than 10 mA, even more preferably lessthan 5 mA, and even more preferably less than 2 mA.

EXAMPLES

The following examples are offered to aid in understanding of thepresent invention and are not to be construed as limiting the scopethereof. Unless otherwise indicated, all parts and percentages are byweight. Also, unless otherwise noted, the methods described in the TestMethodology section were utilized.

Example 1 Acrylic-Modified Polyurethane Dispersion

The following materials were charged to a two-liter flask equipped withan agitator, a thermocouple, a condenser, and a gas inlet port:

PS-70L polyester diol (Stepan Company, 159.15 grams Northfield, IL)TERATHANE T-2000 polytetrahydrofuran 53.04 grams (E. I. du Pont)Dimethylol propionic acid 42.67 grams DESMODUR W diisocyanate (BayerMaterialScience) 151.36 grams Methyl methacrylate 155.49 grams PROGLYDEDMM glycol ether (Dow Chemical) 75.32 grams Butylated hydroxy toluene0.64 grams

These materials were then agitated with an air sparge and gently heatedto 88° C. The reaction was held at 88° C. for approximately 3 hours toreach completion, which was determined by isocyanate titration. Thematerial was then cooled to 60° C. and 32.16 grams of Triethylamine wereadded to the flask and mixed. After 5 to 10 minutes of mixing, thecontents of the flask were slowly transferred to a second reactionvessel containing 1001.57 grams of deionized water and 75.32 grams ofPROGLYDE DMM.

The second reaction vessel was equipped with an agitator, athermocouple, a gas inlet port and a condenser. The contents of thesecond reaction vessel were agitated vigorously throughout the additionof the contents of the first reaction vessel. The initial temperature ofthe contents of the second reaction vessel was 9-12° C. The contents ofthe first reaction vessel were transferred to the second reaction vesselover the course of approximately 15 minutes.

Immediately following the completion of the transfer of polymer from thefirst reaction vessel to the second reaction vessel (i.e., thedispersion vessel), a premix of 33.0 grams deionized water and 7.22grams ethylene diamine was added to the second reaction vessel. Theresulting batch was agitated for 45 minutes after the addition and amild exotherm of 3-5° C. was observed. After 45 minutes of elapsed time,196.08 grams of n-butyl acrylate and 41.42 grams of glycidylmethacrylate were added with agitation. and a nitrogen blanket wasapplied to the reactor. The batch was agitated for 15 minutes and 1.33grams of tert-butyl hydroperoxide (70% aq.) was added.

Immediately after this addition a feed of the following premix wasstarted:

Erythorbic Acid 1.07 grams Deionized Water 40.0 grams Triethylamine 1.20grams 7% aqueous solution of DISSOLVINE E-FE-13 0.06 grams iron catalyst(Akzo Nobel)

This premix was fed at an even rate over 30 minutes with an additionfunnel. At approximately 10 to 15 minutes into the feed, an exothermoccurred. The batch was allowed to increase in temperature and the peaktemperature attained was 50-60° C. After the feed of the premix wascomplete, the addition funnel was rinsed with 10.0 grams of deionizedwater. The batch was then cooled and poured.

Example 2 Coating Composition

Coating compositions 2A and 2B were prepared by combining theingredients listed below in Table 1.

TABLE 1 Ingredients Example 2A (wt-%) Example 2B (wt-%) Ex. 1Composition 78.61 75.20 Propylene Glycol 11.78 11.27 Deionized Water7.87 8.53 Carnabua Emulsion 1.74 1 Phenolic Crosslinker — 3.33

Coating compositions 2A and 2B each had a theoretical total solidscontent of about 30 wt-%. The nonvolatile content of coating composition2A was 98.8 wt-% of Example 1 solids and 1.2 wt-% of lubricant solids.The nonvolatile content of coating composition 2B was 93.42 wt-% ofExample 1 solids, 5.48 wt-% phenolic crosslinker solids, and 1.1 wt-%lubricant solids.

Example 3 Coating Properties

The coating compositions of Examples 2A and 2B were each applied as acoil coating to Alcoa chrome metal coil. Steps were taken to improveflow and leveling prior to a 10-second dwell in an oven to achieve a465° F. (241° C.) peak metal temperature and cure the coating.

The cured coating samples obtained in Example 2 for coating compositions2A and 2B were tested for a variety of coating properties. The data forsome of the coating property tests are included in Table 2 below.

TABLE 2 Coating Composition Example 2A Example 2B Film Weight (mg/in²)6.9 6.7 MEK Resistance 2 7 Feathering* 0 0 Water Pasteurization (90minutes at 250° F. (121° C.)) Blush (water/water vapor)  8/10  8/10Adhesion (water/water vapor) 10/10 10/10 202 Beverage Can Ends Initial(prior to Dowfax)  5.9 mA 0.5 mA After Dowfax 13.6 mA 0.9 mA *Featheringdata is reported in inches. Pasteurization was conducted for 45 minutesat 185° F. (85° C.) prior to testing for feathering.

The complete disclosure of all patents, patent applications, andpublications, and electronically available material cited herein areincorporated by reference. The foregoing detailed description andexamples have been given for clarity of understanding only. Nounnecessary limitations are to be understood therefrom. The invention isnot limited to the exact details shown and described, for variationsobvious to one skilled in the art will be included within the inventiondefined by the claims. In some embodiments, the invention illustrativelydisclosed herein may be suitably practiced in the absence of any element(e.g., process step, ingredient, etc.) that is not specificallydisclosed herein.

What is claimed is:
 1. An article, comprising: a food or beverage can,or a portion thereof, comprising: a metal substrate; and a cured coatingdisposed on at least a portion of the metal substrate, the cured coatingformed from a coating composition comprising: an aqueous dispersion of apolyurethane-urea polymer, and a vinyl polymer.
 2. The article of claim1, wherein the polyurethane-urea polymer includes salt groups.
 3. Thearticle of claim 1, wherein the polyurethane-urea polymer has a numberaverage molecular weight greater than 5,000, and wherein thepolyurethane-urea polymer is formed using at least 1% by weight of anisocyanate compound.
 4. The article of claim 1, whereinpolyurethane-urea polymer is present in an amount of at least 5 wt-%,based on the total weight of the vinyl polymer and polyurethane-ureapolymer, and wherein the vinyl polymer is present in an amount of atleast 15 weight percent, based on the total weight of the polymer andpolyurethane-urea polymer.
 5. The article of claim 1, wherein thepolyurethane-urea polymer includes at least about 5 urea linkages. 6.The article of claim 1, wherein the polyurethane-urea polymer includesone or more unsaturated polycyclic groups.
 7. The article of claim 1,wherein the coating composition, when present on an aluminum beveragecan end at a dry film thickness of 7 milligrams per square inch, passesless than 5 milliamps of current after being exposed for 4 seconds to aroom-temperature electrolyte solution containing 1% by weight of NaCldissolved in water.
 8. The article of claim 1, wherein thepolyurethane-urea polymer is the reaction product of: a polyurethaneprepolymer having a number average molecular weight of from 2,000 to6,000 and at least one isocyanate group, and a polyamine.
 9. The articleof claim 8, wherein the polyurethane polymer includes one or morealiphatic carbon-carbon double bonds.
 10. The article of claim 9,wherein the one or more aliphatic double bonds are present in one ormore groups formed from functionalized butadiene or polybutadiene. 11.The article of claim 1, wherein the vinyl polymer has a number averagemolecular weight of at least 100,000.
 12. The article of claim 11,wherein at least 40 weight percent of the vinyl polymer comprises analkyl acrylate, alkyl methacrylate, or a combination thereof, based onthe total non-volatile weight of ingredients used to make the vinylpolymer, and wherein the coating composition is substantially free ofbound bisphenol A and aromatic glycidyl ether compunds.
 13. An article,comprising: a food or beverage can, or a portion thereof, comprising: ametal substrate; and a cured coating disposed on at least a portion ofthe metal substrate, the cured coating formed from a coating compositioncomprising: an aqueous dispersion of a polyurethane polymer having oneor more aliphatic carbon-carbon double bonds, and a vinyl polymer. 14.The article of claim 13, wherein the one or more aliphatic double bondsare present in one or more groups formed from functionalized butadieneor polybutadiene.
 15. The article of claim 14, wherein a latex polymerincludes both the polyurethane polymer and the vinyl polymer.
 16. Thearticle of claim 13, wherein the polyurethane polymer and the vinylpolymer are linked to one another by one or more covalent linkages. 17.The article of claim 16, wherein a latex polymer includes both thepolyurethane polymer and the vinyl polymer.
 18. The article of claim 16,wherein the one or more covalent linkages comprises a carbonate ester,epoxy, ether, imide, imine, or urea linkage.
 19. The article of claim16, wherein the one or more covalent linkages are hydrolytically stablecovalent linkages.
 20. The article of claim 16, wherein the coatingcomposition is present on a food-contact surface of the metal substrate.